TLDR;
- Most paid ads agencies are useless for B2B SaaS because they're generalists who don't understand long sales cycles, LTV, or complex customer journeys. They'll try to apply an eCommerce model that will burn your cash.
- Red flags to watch for include promising guaranteed results, focusing on vanity metrics like clicks, and showing irrelevant case studies. If they can't talk about CAC, LTV, and churn, run.
- The right agency for a UK SaaS business will be a specialist, have deep experience in the London tech scene, and challenge your assumptions. Their initial consultation should feel like a free strategy session, not a sales pitch.
- Your most powerful metric isn't CPL, it's your LTV to CAC ratio. You must know your numbers before you even speak to an agency. Use the interactive LTV calculator in this guide to figure it out.
- Finding the right partner is hard work. This guide includes a vetting flowchart and the exact questions to ask to seperate the experts from the cowboys.
I see this all the time. A UK-based SaaS founder, sharp as a tack, has built a brilliant product. They've raised a bit of money, or they're bootstrapping with real traction, and they decide it's time to pour some fuel on the fire with paid ads. So they hire an agency. Six months and £50,000 later, they have a handful of low-quality leads, a dashboard full of meaningless 'impressions', and a deep-seated conviction that "paid ads don't work for us".
They're wrong. Paid ads almost certainly *do* work. The problem isn't the channel; it's that they hired the wrong agency. The vast majority of paid advertising agencies, especially the generalists you find with a quick Google search, are fundamentally unfit to handle B2B SaaS accounts. They don't have the experience, they don't understand the metrics, and honestly its just not their area of expertise. If you're struggling with this, you're not alone, and the good news is that it's a solvable problem. But first, you need to understand why your search for a good partner feels so difficult and how to find the right B2B SaaS marketing agency in London specifically.
So, Why Are Most Agencies Rubbish for SaaS?
The core issue is a mismatch in business models. Most agencies cut their teeth on eCommerce or local lead generation. Their entire worldview is built around a simple, short-term feedback loop: Spend £1, get £3 back in sales this week. Job done. Their reporting is centred on Return on Ad Spend (ROAS), and their strategies are geared towards impulse buys.
B2B SaaS is a completely different beast.
Your sales cycle isn't 30 minutes; it's 3, 6, or even 12 months. Your 'customer' isn't one person but a buying committee of five. Your success isn't measured by a single transaction but by Lifetime Value (LTV) and monthly recurring revenue (MRR). A user might sign up for a free trial today and not become a paying customer for 90 days. The ROAS-obsessed eCommerce agency looks at this and sees a failing campaign. They don't have the patience or the framework to measure what actually matters.
They don't understand that a £250 'lead' from a Head of Engineering at a FTSE 250 company, who might eventually sign a £50k annual contract, is infinitely more valuable than 100 £2.50 'leads' from tyre-kickers who will never convert. They will optimise for the cheap leads every single time, because it makes their reports look good in the short term, and in doing so, they'll completely torpedo your growth. This is the fundamental reason so many founders end up believing they need to stop wasting money on B2B SaaS ads, when in reality they just need a better pilot.
When you layer on the specifics of the UK market, particularly in hubs like London, the problem gets worse. The competition is fierce, CPCs are high, and decision-makers are cynical and bombarded with marketing messages. A generic approach that might get some traction in a less mature market will get you absolutely nowhere here. You need a partner who understands this specific battleground.
The Glaring Red Flags That Should Make You Run
Vetting agencies can feel overwhelming, but it gets easier when you know what to look for. Think of this as your field guide to spotting the cowboys. If you encounter any of the following, end the conversation politely and move on.
1. The "Guaranteed Results" Promise
This is the number one sign of an amateur or a charlatan. Anyone who promises you a specific ROAS or a fixed number of leads is either lying or deeply incompetent. There are far too many variables in paid advertising – your offer, your landing page, your sales process, market shifts, competitor actions, platform algorithm changes. No professional would ever make such a guarantee. What they *should* be able to do is show you case studies from similar SaaS businesses and talk about the *process* they used to get those results. For instance, I remember one campaign we ran for a software client that achieved a CPL of around $22 for B2B decision-makers on LinkedIn, but we'd never guarantee that exact result for a new client without understanding their specific offer and market.
2. Obsession with Vanity Metrics
During the discovery call, listen carefully to the language they use. Are they talking about clicks, impressions, and click-through rates (CTR)? Or are they asking about your Customer Acquisition Cost (CAC), Lifetime Value (LTV), trial-to-paid conversion rate, and sales cycle length? If it's the former, they are a 'top of the funnel' agency. They see their job as just driving traffic. A true SaaS partner knows their job isn't done until that traffic converts to MRR. They should be just as interested in your HubSpot dashboard as your Google Ads account.
3. Irrelevant Case Studies
"We got a 10x ROAS for this women's apparel brand!" Great. What does that have to do with your complex FinTech platform? It's a completely different skill set. Ask to see case studies for B2B SaaS companies, preferably in a similar space or with a similar Average Contract Value (ACV) to yours. Don't be afraid to dig in. Ask them to walk you through the strategy. Why did they choose LinkedIn over Google Search for that client? What was the offer that worked? What audiences failed? If they can't answer these questions in detail, the case study probably isn't theirs, or it was a fluke. A good agency will be proud to show you a campaign where they generated 1,535 trials for a B2B SaaS client, and explain the strategy that made it happen.
4. The "Secret Sauce" or "Proprietary System"
Some agencies will try to dazzle you with talk of their unique, black-box system. This is usually nonsense designed to prevent you from understanding what they're actually doing. Effective paid advertising isn't magic; it's a rigorous process of research, testing, and analysis. A good partner will be transparent about their process. They should be able to explain their methodology for audience research, campaign structure, creative testing, and optimisation. They should be teaching you, not hiding the ball.
To help you visualise this vetting process, here's a simple flowchart. If you hit a red box, it's a hard no.
The Million-Pound Question: What's Your LTV?
Before you even dream of hiring an agency, you need to do your own homework. The single most important peice of information you must have is your customer Lifetime Value (LTV). An agency can't possibly set a sensible Customer Acquisition Cost (CAC) target if you don't know what a customer is worth to you. This isn't their job to figure out; it's yours.
Forget trying to get the 'cheapest' leads. That's a race to the bottom that leads to low-quality users who churn quickly. The real goal is to acquire high-value customers profitably. A healthy SaaS business typically aims for an LTV to CAC ratio of at least 3:1. This means for every £1 you spend to acquire a customer, you should expect to get at least £3 back in lifetime gross margin. Armed with this ratio, you can have a much more intelligent conversation. This is the kind of commercial thinking we talk about in our playbook for CFOs on measuring ad ROI.
To make this tangible, let's calculate it. You need three numbers:
- Average Revenue Per Account (ARPA): The average amount you collect per customer, per month.
- Gross Margin %: Your revenue minus the cost of goods sold (COGS), which for SaaS is mostly things like hosting, support, and third-party API costs.
- Monthly Churn Rate %: The percentage of customers you lose each month.
Here's an interactive calculator to help you figure out your LTV and a sensible target CAC. Play around with the numbers to see how small changes in churn or ARPA can dramatically affect how much you can afford to spend on ads.
What Actually Works for B2B SaaS in the UK?
Once you've weeded out the bad fits and you know your numbers, the conversation shifts to strategy. For B2B SaaS in a competitive market like the UK, you can't just throw up a few ads on Facebook and hope for the best. You need a considered, multi-channel approach. The debate often comes down to two main players for high-value leads: Google Ads and LinkedIn Ads.
Google Search Ads are brilliant for capturing intent. You're targeting people who are *actively searching* for a solution to their problem. Keywords like "best accounting software for small business" or "cybersecurity compliance platform" are pure gold. These leads are often high quality because they have an immediate need. The downside is that it's an auction, and in the UK, those keywords can be punishingly expensive. Success here relies on masterful keyword research, tight campaign structure, and a landing page that converts like crazy. We've written an entire playbook on how to approach Google Ads for UK B2B SaaS.
LinkedIn Ads are for creating demand. Your ideal customer might not be searching for you, but you know who they are. LinkedIn's targeting is unparalleled for B2B – you can target by job title, company size, industry, seniority, and even specific company names. You can get your message directly in front of the Head of IT at Barclays. The leads can be more expensive on a pure CPL basis, but their quality and potential value can be much higher. The key here is a compelling offer and creative that speaks directly to their pain points, not just your features.
Often, the best strategy involves a combination of both. You can read a more detailed comparison in our London-specific guide to Google Ads vs. LinkedIn. Here’s a quick overview of how these platforms stack up for a typical London-based SaaS company.
Making the Decision: Your Final Checklist
You've done the pre-vetting, you know your LTV, and you've had a few initial calls. Now it's time to make a decision. The right choice could be the difference between stagnating and hitting your next growth target. The wrong choice means more wasted cash and frustration.
This isn't about finding the cheapest option or the one with the slickest sales deck. It's about finding a genuine partner who will function as an extension of your marketing team. They should be strategic, data-driven, and brutally honest with you. If they aren't pushing back on your ideas and challenging your assumptions, they aren't doing their job.
For more on this, our ultimate guide to vetting UK B2B ad consultants goes even deeper into the questions you should be asking.
This is the main advice I have for you:
| Vetting Stage | Actionable Step | What You're Looking For |
|---|---|---|
| 1. Initial Research | Review their website and case studies. Look for specific B2B SaaS client examples with real metrics (trials, pipeline, revenue), not just vanity numbers. | Evidence of specialisation. Do they 'speak SaaS'? Do their results resonate with your business model? |
| 2. The Discovery Call | Come prepared with your LTV and target CAC. Ask them tough questions about strategy, process, and past failures. | They should ask more questions about your business than they talk about themselves. Look for strategic thinking, not a sales pitch. |
| 3. The Proposal | Analyse the strategy they propose. Is it a generic template or is it customised to your specific ICP, offer, and market position? | A clear, logical plan of action for the first 90 days. It should outline research, campaign builds, testing methodology, and reporting cadence. |
| 4. The "Gut Check" | Ask yourself: "Do I trust this person/team to spend my money wisely? Do I believe they can challenge me to be better?" | Confidence and chemistry. You need a partner you can have honest, difficult conversations with about performance. |
Finding the right agency is a significant investment of your time, and it should be. The alternative is far more costly. If you choose correctly, you gain more than just a media buyer; you gain a strategic growth partner who can help you navigate the complexities of scaling in the competitive UK market.
If this process feels daunting, it's because it is. This is what we specialise in. We work exclusively with B2B businesses, many of them SaaS companies just like yours, to build and scale profitable advertising campaigns. If you'd like an expert second opinion on your current strategy or help building one from scratch, feel free to schedule a free, no-obligation consultation call. We'll give you honest, actionable advice you can implement immediately, whether you decide to work with us or not.
