SaaS Launch in London: The Ultimate Agency Vetting Guide

Right then. You're launching a SaaS product in London. The pressure's on, the runway's probably shorter than you'd like, and you know that getting those first paying customers is everything. You've wisely decided that burning your own cash trying to figure out paid advertising is a mug's game, so you're looking for 'SaaS product launch services'. Good start. But the problem is, most of what you'll find is noise. You're about to walk into a minefield of generalist agencies who think running ads for a SaaS business is the same as for an eCommerce store. It absolutely is not.

The truth is, launching a SaaS product with paid ads, especially in a hyper-competitive hub like London, requires a very specific skillset. It's less about flashy creative and more about cold, hard maths, deep customer psychology, and a ruthless focus on the right metrics. Most agencies will happily take your money and deliver clicks and 'brand awareness'. What you need are trial sign-ups, demos with genuinely interested prospects, and ultimately, paying users that stick around. This guide is designed to help you tell the difference between a partner who can help you build a scalable acquisition engine and one who will simply set your money on fire. Getting this decision right is probably one of the most important you'll make in your go-to-market strategy.

Why is launching a SaaS product in London so bloody expensive?

First, let's get one thing straight. The London market is a different beast entirely. You've got global financial institutions in the City, a sprawling tech scene around Old Street's 'Silicon Roundabout', and thousands of ambitious businesses all competing for the same eyeballs. This means one thing: you're going to pay a premium. Your cost-per-click (CPC) on Google Ads and cost-per-mille (CPM) on LinkedIn will be significantly higher than in Manchester, let alone Warsaw or Lisbon. Anyone who tells you otherwise is either lying or has never actually run a serious B2B campaign here.

But it's not just about cost. It's about sophistication. The decision-makers you're trying to reach—the CTOs, the Heads of Sales, the Finance Directors—are bombarded with pitches all day long. They have highly attuned BS-detectors. A generic ad with a stock photo and bland copy like "Revolutionise your workflow" will be scrolled past without a second thought. Your messaging has to be precise, insightful, and speak directly to a pain they are feeling *right now*.

However, the prize for getting it right is enormous. A single enterprise customer won in Canary Wharf could have a lifetime value in the tens or even hundreds of thousands of pounds. The concentration of high-value B2B customers is why you're here. The challenge is acquiring them profitably. You can't afford to waste your budget reaching the wrong people. An agency that understands this will talk less about 'getting your name out there' and more about ruthless efficiency and targeting. They know that in London, you don't hunt with a shotgun; you hunt with a sniper rifle.

How do I spot an agency that actually knows SaaS?

This is the most important filter you will apply. When you get on that initial call, they'll show you a lovely presentation with their logo and talk about their "proprietary process." Ignore all of it. Ask them one question: "Can you show me case studies for B2B SaaS companies you have helped launch or scale?"

If they hesitate, or show you results for a fashion brand, a local plumber, or even a B2C app, the conversation is over. Thank them for their time and hang up. Their expertise is irrelevant to you. The dynamics of SaaS user acquisition are fundamentally different.

A true SaaS specialist will be eager to show you the right kind of results. For one software client, we generated 5,082 trials at just $7 per trial using Meta Ads. For another, a medical job matching platform, we reduced their cost per user acquisition from a painful £100 down to just £7. Those are the kinds of conversations you want to be having. We are not talking about vanity metrics like 'impressions' or 'clicks'. We are talking about business results.

Here's what to look for in their case studies:

• -> The Right Metrics: Are they talking about Cost Per Trial, Cost Per Demo, Cost Per MQL/PQL, or are they talking about Click-Through Rate (CTR)? CTR is a means to an end, not the goal itself. You need an agency that is obsessed with the cost to acquire a potential customer, not just a visitor.
• -> Understanding of the Funnel: Do they talk about the entire funnel? How they used retargeting to bring back people who dropped off during signup? How they built lookalike audiences from the client's best existing customers? This shows they understand the SaaS customer journey isn't a single click.
• -> Platform Specificity: Did they get their results from the right places? For B2B SaaS, this is usually LinkedIn and Google Search, with Meta (Facebook/Instagram) playing a role for specific niches and retargeting. If they're talking about getting amazing results on TikTok for a financial compliance SaaS, you should be very sceptical.
• -> Real Numbers: Vague statements like "we increased their leads" are a red flag. Look for concrete numbers. "We generated 1,535 trials for a B2B SaaS client using Meta ads" is a statement of fact. It's specific and demonstrates real experience. You need a partner that lives and breathes this stuff, and the details in their case studies will tell you everything you need to know. A good place to start your evaluation is our London agency vetting guide.

What questions should I ask them to expose their real strategy?

Once an agency has passed the case study test, you need to dig into their strategic thinking. A mediocre agency will ask you, "So, who is your target audience?" and you'll say "SMEs in the finance sector." They'll nod, write it down, and go off to target 'Finance Director' job titles on LinkedIn. This is lazy, expensive, and rarely works.

A great agency understands that your Ideal Customer Profile (ICP) isn't a demographic; it's a person with a career-threatening nightmare. They will ask questions that get to the heart of that problem. They need to understand the pain so they can craft a message that resonates.

Instead of you answering their questions, turn it around and ask them:

• -> "Walk me through your process for understanding our customer's core problem. How do you get beyond job titles?"
• -> "What kind of ad copy angle would you test first for us, and why?"
• -> "Where else would you look for our audience, beyond the obvious LinkedIn targeting?"

Their answers will tell you everything. A great agency will talk about finding the 'watering holes'. Where does your ICP hang out online? What newsletters do they actually read (like Stratechery)? What podcasts do they listen to on their commute (like Acquired)? What industry influencers do they follow on Twitter? This is the intelligence that allows them to build a truly targeted campaign, not just a broad demographic bucket. They'll talk about building a paid acquisition framework based on deep customer insight.

Tbh, if an agency's first questions to you aren't deeply probing ones about your customer, your product, and your business model, they see you as just another monthly retainer. The right partner sees you as a growth puzzle they are genuinely excited to solve. They should be challenging you, questioning your assumptions, and demonstrating a level of curiosity that goes far beyond a surface-level understanding of your business.

How do I know if their proposed budget and goals are realistic?

This brings us to the maths. Many founders get fixated on a low Cost Per Lead (CPL). The real question isn't "How low can my CPL be?" but "How high a CPL can I afford to acquire a fantastic customer?". The answer lies in your Customer Lifetime Value (LTV). An agency that doesn't insist on understanding your LTV before they talk about ad spend is just guessing.

The calculation is quite simple, but it's the foundation of a scalable SaaS business. You need three numbers:

1. Average Revenue Per Account (ARPA): What's the average amount a customer pays you each month?
2. Gross Margin %: What's your profit margin on that revenue after accounting for costs like servers and support?
3. Monthly Churn Rate: What percentage of your customers cancel their subscription each month?

The formula is: LTV = (ARPA * Gross Margin %) / Monthly Churn Rate

Let's say your ARPA is £200, your Gross Margin is 80%, and your monthly churn is 5%.
LTV = (£200 * 0.80) / 0.05
LTV = £160 / 0.05 = £3,200

This means, on average, each customer you acquire is worth £3,200 in gross margin to your business over their lifetime. A healthy LTV to Customer Acquisition Cost (CAC) ratio is at least 3:1. This means you can afford to spend up to £1,066 (£3,200 / 3) to acquire a single new customer. If your sales process converts 1 in 10 qualified trials into a customer, you can afford to pay up to £106 per trial signup. Suddenly that £50 CPL from a highly targeted LinkedIn campaign doesn't look so bad, does it? It looks like a bargain. This is the maths that unlocks aggressive growth and should be central to any conversation about your paid advertising budget.

Why should I be wary of agencies obsessed with 'Booking Demos'?

Now we get to the offer. This is where so many B2B ad campaigns fall flat. The default call-to-action for most is "Request a Demo". Frankly, it's an arrogant and outdated approach. It presumes your prospect, a busy decision-maker, wants to schedule a 30-minute meeting to be sold to. It's a high-friction, low-value proposition that immediately puts them on the defensive.

The best SaaS companies, and by extension the best agencies, understand the power of Product-Led Growth (PLG). Your product should be your best salesperson. The goal of your advertising shouldn't just be to book a meeting; it should be to get a prospect to experience a moment of value from your product as quickly as possible. This creates a Product Qualified Lead (PQL), someone who has already seen that your tool can solve their problem. This is infinitely more valuable than a Marketing Qualified Lead (MQL) who just downloaded a whitepaper.

A forward-thinking agency will challenge your reliance on the "Request a Demo" button. They will brainstorm with you on creating better, lower-friction offers:

• -> A genuinely free trial (no credit card): This is the gold standard. Let them get their hands on the product and see the value for themselves.
• -> A freemium plan: Let them use a core part of your product for free, forever. The usage itself becomes the upsell engine.
• -> A valuable, interactive tool: If a free trial isn't feasible, can you offer a free tool that solves a small part of their problem? A marketing agency might offer a free SEO audit tool. For our agency, we offer a free 20-minute strategy session where we actually audit their failing ad campaigns and give them actionable advice.

If an agency's only idea is to run ads to a landing page with a "Request a Demo" form, they're stuck in the past. You need a partner who thinks like a growth strategist, not just a media buyer. This is a core part of a modern founder's go-to-market framework.

What ad platforms should a good agency even be talking about?

For a B2B SaaS launch in London, the conversation should revolve around a few core platforms. An agency's recommendations here will reveal their level of expertise in your specific niche.

Google Ads: This is about capturing intent. You're targeting people who are actively searching for a solution to their problem. A savvy agency won't just target broad terms like "accounting software". They'll focus on high-intent, long-tail keywords that signal a user is ready to buy, like "xero alternative for UK agencies" or "best ap automation software for smes". The competition for these terms in the UK is fierce, so a deep understanding of bidding strategies, negative keywords, and ad copy that stands out is absolutely essencial. For any SaaS founder in London, understanding this platform is a must, and our guide to Google Ads for London B2B SaaS is a good starting point.

LinkedIn Ads: This is the most obvious platform for B2B targeting. The ability to target by job title, company size, industry, and even specific company names is unparalleled. However, it's also the most expensive. A lazy agency will burn through your budget here in days with poor results. A smart agency will have strategies to manage the high cost. They'll talk about:

• -> Testing Lead Gen Forms (which pre-fill a user's details) versus sending traffic to a landing page. Lead Gen Forms often have a lower CPL but the lead quality can be lower. It's a trade-off that needs testing.
• -> Using more engaging ad formats like video or carousel ads to better qualify prospects before they click.
• -> Building highly specific, narrow audiences. We've seen campaigns for B2B decision makers deliver leads for as low as $22, which is fantastic for this platform, but it requires meticulous setup.

Meta Ads (Facebook/Instagram): Many people dismiss Meta for B2B, and that's a mistake. A specialist agency knows its hidden strengths. While direct targeting isn't as good as LinkedIn, you can be very effective by:

• -> Uploading a list of your ideal target companies or existing customers and creating a hyper-targeted custom audience.
• -> Building powerful Lookalike Audiences from your best customers. You're telling Meta's algorithm "go find me more people who look exactly like my highest LTV users." This is often far more effective than manual interest targeting.
• -> Targeting interests related to competitor software, industry publications, or influencers. For instance, you could target people interested in 'HubSpot' or 'SaaStr'.

What are the biggest red flags on that first agency call?

You're on the call. You've seen their case studies. You've discussed strategy. Now, listen carefully to how they talk. Certain phrases should set off alarm bells.

Red Flags 🚩:

• -> "We guarantee a 5x ROAS." No one can guarantee results in paid advertising. There are too many variables. This is a sales tactic used by people who will likely underdeliver. Real experts talk in terms of probabilities, benchmarks, and a methodical testing process.
• -> They don't ask about your LTV, churn, or sales cycle. If they aren't interested in your business economics, how can they possibly run a profitable campaign for you? They're just focused on spending your ad budget.
• -> They push for a 12-month contract upfront. A confident agency will be happy to start with a 3-month pilot project to prove their value. They'll want to earn your long-term business, not lock you into it.
• -> They ask for references after you've seen case studies and had a strategy call. Tbh, this is a red flag for us. If our detailed case studies and the free, in-depth strategy audit we provide aren't enough to build trust, it signals a fundamental misalignment that will likely cause problems down the line.

Green Lights ✅:

• -> They offer to do a free audit of your existing ad accounts or analytics. This shows they're willing to provide value upfront and are confident they can find areas for improvement.
• -> They challenge your assumptions. "Have you considered that your pricing might be an issue?" or "Are we sure this is the right ICP to go after first?" This shows they are thinking like a partner, not a vendor.
• -> They talk about starting with a small, focused test. "Let's validate this one channel and audience with a £2k budget before we scale." This is a sensible, data-driven approach that respects your capital.
• -> They spend most of the call asking you questions. They are genuinely curious and trying to understand your business inside and out. This is the foundation of any succesful partnership.

So, how do I make the final decision?

Choosing an agency to handle your SaaS launch in London is a massive decision. It's not just about hiring a supplier; it's about finding a growth partner who has the specific, niche expertise to navigate this uniquely challenging market. You need a team that thinks beyond clicks and impressions, one that understands SaaS economics, obsesses over your customer's pain, and has a proven track record of turning ad spend into tangible business growth.

Don't be swayed by a slick sales pitch or a low management fee. The cost of hiring the wrong agency isn't just their fee; it's the wasted ad spend and, more importantly, the months of lost time on your runway that you can never get back. Be thorough in your vetting, ask the tough questions, and trust your gut. The right partner will feel less like they're selling to you and more like they're already on your team, strategising how to win.

I've detailed my main recommendations for you below:

Navigating this on your own can be a daunting and expensive process of trial and error. If you'd like an expert second opinion on your launch strategy or want to see how a specialist team would approach your specific challenges, consider organising a free, no-obligation strategy session. We can audit your current plans and provide actionable advice you can implement immediately, whether you decide to work with us or not.