The UK SaaS Founder's Guide To Paid Ad Agencies

I see this question come up a lot. You're a UK SaaS founder, you've built something brilliant, and now you need to get it in front of the right people. So you start looking for a paid ads agency, and you quickly realise something's wrong. They all talk about ROAS, shopping campaigns, and quick wins. Their case studies are full of fashion brands and subscription boxes. They just don't seem to get it.

And you're right, they don't. The brutal truth is that the vast majority of paid ad agencies in the UK are built on an e-commerce model. They're geared for high-volume, low-consideration products with a 30-day attribution window. Trying to apply that thinking to B2B SaaS is like trying to use a hammer to perform surgery. It's messy, ineffective, and you'll probably do more harm than good. You need a specialist, but finding one feels impossible.

This isn't another generic guide. This is a playbook for UK SaaS founders, written from years of being in the trenches, running and scaling campaigns for software companies. I'm going to show you how to cut through the noise, ask the questions that make generalists squirm, and identify a partner that actually understands how to grow a SaaS business with paid advertising.

So, why do most agencies get SaaS marketing completely wrong?

It comes down to a fundamental misunderstanding of the business model. An e-commerce business sells a product. A SaaS business sells a relationship. The entire customer journey is different, and that has massive implications for how you should advertise.

Think about the last time you bought a pair of trainers online. You saw an ad, you clicked, you liked the look of them, maybe you waited for a discount code, and then you bought them. The whole process, from first click to purchase, might have taken a day or two. The agency's job is simple: get the cost of that sale lower than the profit on the trainers. They can measure success with a simple metric: Return on Ad Spend (ROAS).

Now think about buying a new piece of software for your business. Let's say it's a new project management tool. The process looks nothing like buying trainers. First, someone on your team identifies a problem – projects are late, communication is a mess. They start researching solutions. They read reviews, compare features, and shortlist a few options. Then they need to get buy-in from their manager. Maybe you need a demo for the whole team. Then it has to go to finance for approval. The sales cycle could take three, six, even twelve months. There are multiple decision-makers involved. It's a considered purchase, not an impulse buy.

A generalist agency sees this long, complex process and their brain short-circuits. Their model is built for speed and simplicity. They don't know how to track a lead over a six-month sales cycle. They don't know how to create ads that speak to a Head of Engineering's deep-seated fear of technical debt, while also creating a business case that resonates with a CFO. They just throw up some generic ads pointing to a "Request a Demo" page and wonder why the CPL is £200 and none of the leads are closing. It's a completely different discipline.

What should I actually be looking for in an agency's case studies?

This is where you seperate the contenders from the pretenders. When you look at an agency's case studies, you need to be ruthless. Don't be impressed by big revenue numbers or flashy logos. Look for the details that show they understand SaaS.

First, are there any SaaS clients at all? If it's all clothing brands and gadgets, close the tab. It's not a good fit. If they do have SaaS case studies, you need to dig deeper. Are they B2C SaaS (like a meditation app) or B2B SaaS (like your accounting software)? They're very different beasts. We've worked on both, and the strategies are worlds apart. For one app client in the events space, we generated over 45,000 signups at under £2 per signup across Meta, TikTok, and Apple Ads. That's a great result for a B2C app, but that CPA would be unsustainable for a high-touch B2B product.

Next, look at the metrics they're proud of. Are they talking about ROAS? That's a red flag. As we've established, ROAS is almost meaningless for a subscription business. You're not looking for a return on the first month's payment; you're looking for a return over the entire lifetime of the customer. A true SaaS agency will talk about metrics like:

• -> Cost Per Trial / Cost Per Sign-up: How much does it cost to get someone to actually try the product? For one B2B software client, we generated over 5,000 trials at about £5.50 each from Meta Ads, which was a fantastic result for them.
• -> Cost Per Qualified Lead (CPL): Not just any lead, but a lead that meets specific criteria. We've run LinkedIn campaigns for B2B decision makers where the CPL was around $22, or about £17. Higher than a simple email signup, but the quality was far superior.
• -> Customer Acquisition Cost (CAC): The total cost to get a paying customer. This is the big one.
• -> Lifetime Value (LTV): How much gross margin a customer generates over their entire time with you.
• -> LTV:CAC Ratio: This is the holy grail. A healthy SaaS business typically aims for a ratio of 3:1 or higher. This means for every £1 you spend acquiring a customer, you get £3 back in gross margin.

If an agency can't talk fluently about these metrics, they haven't worked seriously with SaaS clients. They should be able to show you how they've moved the needle on these specific KPIs. I remember one medical job matching SaaS we worked with. When they came to us, their CPA was over £100. Working on their Google and Meta campaigns, we brought it down to just £7. That's the kind of impact a specialist can have.

Finally, look for evidence of scale. It's one thing to get a few cheap leads with a small budget. It's another thing entirely to maintain performance as you increase spend. Ask them to talk you through a time they scaled a SaaS client's budget. What happened to the CAC? What new channels did they introduce? What broke? Their answer will tell you everything you need to know about their real-world experience. Many founders come to us because they've hit a plateau; they can't scale spend without their CPA going through the roof. This is a normal problem, and a good agency will have a clear methodology for breaking through it by systematically testing new audiences, creatives, and improving funnel conversion rates.

How do I know if they *really* understand my customer?

This is the most important question. You can teach someone the mechanics of Google Ads. You can't teach them empathy for your customer. A great SaaS agency is obsessed with your Ideal Customer Profile (ICP), but not in the way you might think.

Forget the generic profiles: "Sarah, 35-45, Head of Marketing at a 50-200 person tech company." This is useless. It leads to bland, generic advertising that speaks to no one. A true expert knows that your ICP isn't a demographic; it's a nightmare. It's a specific, urgent, expensive, career-threatening problem they are facing right now.

Your Head of Engineering client isn't just a job title. She's a leader who lies awake at night terrified that her best developers are going to quit because the deployment process is a broken, manual mess. Your Head of Finance client isn't just looking for 'accounting software'. He's desperately trying to get accurate cash flow projections before the next board meeting because the last set were a work of fiction and his credibility is on the line.

An agency that gets this will ask you questions like:

• -> "What's the one thing that keeps your ideal customer up at night?"
• -> "What 'dumb' solution are they using right now to solve this problem? (e.g., a massive, chaotic spreadsheet)"
• -> "What happens if they fail to solve this problem in the next six months?"
• -> "Who do they need to convince internally to buy a solution like yours?"

Once they understand the pain, their entire approach to targeting changes. On Google Ads, they won't just bid on your brand name. They'll target long-tail keywords that signal deep commercial intent, the kind of phrases someone types when they're actively looking for a solution to their nightmare. Things like "how to reduce engineer onboarding time" or "best way to automate accounts payable". For any UK-based SaaS, understanding the local search landscape is vital, which is why working with a London-based Google Ads specialist who knows B2B SaaS can be a significant advantage.

On LinkedIn, they won't just target job titles. They'll layer on company size, industry, seniority, and even specific skills or group memberships to build a hyper-specific audience that perfectly matches your ICP. We often use this platform to drive high-quality leads, and if you're interested in the specifics, our complete guide to LinkedIn Ads for B2B SaaS breaks down the process in detail.

Their ad copy will change too. It won't list features. It will speak directly to the pain. It'll use the Problem-Agitate-Solve framework. "Is your sales team wasting hours on manual data entry? Are you losing deals because your CRM is a black hole of outdated information? Our platform automates the busywork so your team can focus on what they do best: closing." This is how you stop the scroll and get a click from a busy decision-maker.

What questions should I ask them on a discovery call?

The discovery call is your interview. You're vetting them, not the other way around. Too many founders get on these calls and let the agency run the show with a slick sales presentation. You need to take control and ask questions that reveal their true level of expertise.

Here are a few of my favourites:

1. "Walk me through your process for understanding our ICP's 'nightmare'." - This immediately tests if they've read this article (joking!) but seriously, it forces them to go beyond demographics. A good answer will involve customer interviews, review mining, and analysing sales call transcripts. A bad answer will be "We'll look at your existing customer data."


2. "Our last agency was obsessed with ROAS. How will you measure and report on success for our subscription model?" - This is a layup. The only acceptable answer involves LTV, CAC, and the LTV:CAC ratio. If they hesitate or try to pivot back to ROAS, they're out.


3. "Talk me through a SaaS campaign you scaled from £5k/month to £25k/month. What was the first thing that broke, and how did you fix it?" - This seperates the theorists from the practitioners. Anyone can run a small campaign. Scaling is where things get difficult. Creative fatigues, audiences get saturated, CPAs rise. A real expert will have war stories and a clear process for overcoming these challenges.


4. "What's your opinion on using a 'Request a Demo' button as the main call-to-action on our landing pages?" - A modern, expert SaaS marketer knows this is a high-friction, low-value offer. The best answer will be something like, "It can work for very high-intent traffic, but we'd strongly recommend testing a lower-friction offer like a free trial, a freemium plan, or a valuable content asset to increase our conversion rate and build a pipeline of product-qualified leads."


5. "What channels do you think we should start with and why?" - There is no single right answer here, but their reasoning is what's important. They should justify their choices based on where your ICP spends their time and their stage of awareness. For example, "We'd start with Google Search Ads to capture existing demand from people actively looking for a solution, then use LinkedIn to target specific decision-makers who might not be problem-aware yet." This demonstrates strategic thinking. This whole process is so critical that we've written up a full guide on how UK founders should be vetting paid ad agencies.

Their answers to these questions will be far more revealing than any polished slide deck. Listen for specific, experience-based answers, not vague marketing waffle.

How much should I expect to pay for a specialist UK SaaS agency?

This is the big question, isn't it? The answer is, it depends, but it's probably more than you think, and definately more than the cheap generalist agencies. You're not paying for someone to click buttons in an ad account; you're paying for specialist knowledge, strategy, and experience that can fundamentally change the growth trajectory of your business.

Most specialist agencies work on a monthly retainer model. This could range from £2,000 to £8,000+ per month, depending on the scope of work, the number of channels, and the agency's reputation. Some may also charge a percentage of ad spend (typically 10-15%), often with a minimum retainer. Be very wary of agencies that charge a very low fee; it's often a sign that you'll be handed off to a junior account manager who is learning on your dime.

But the agency fee is only one part of the equation. You also need a healthy budget for the ad spend itself. I usually tell early-stage SaaS founders that they need to be prepared to spend at least £3,000-£5,000 per month on ads to get enough data to make meaningful decisions and see results. Anything less and you're just trickling money away without learning anything.

The real question isn't "how much does it cost?", but "how much can I afford to spend to acquire a customer?". This brings us back to the LTV:CAC ratio. If you know your numbers, you can make an informed decision. This is so important that I've built a simple calculator below to help you figure it out.

When you know you can afford to spend up to £3,333 to acquire a customer that's worth £10,000 to you, suddenly a £2,000 retainer and a £5,000 ad spend doesn't seem so daunting. It's an investment in a predictable growth engine. A good agency isn't a cost centre; they are a profit centre. This focus on unit economics is central to any effective UK SaaS user acquisition strategy.

My final advice: your vetting checklist

Finding the right partner is tough, but it's one of the most important decisions you'll make. To make it easier, I've put my main recommendations into a simple checklist. Use this to score any agency you're considering.

Finding a paid ads agency that truly gets UK B2B SaaS is hard. They are a rare breed. But they do exist. You just have to be incredibly diligent in your search and ruthless in your vetting process. Don't settle for a generalist who promises the world. Look for a specialist who understands your world. Ask the tough questions, focus on the right metrics, and partner with someone who thinks like a SaaS founder, not just a media buyer.

Your business is too important to entrust to someone who doesn't understand its fundamental DNA. Do the work upfront, and you'll find a partner that can become a crucial part of your growth story for years to come.

If you're a UK SaaS founder and this article resonated with you, and you're tired of talking to agencies that don't get it, perhaps it's time for a different conversation. We offer a completely free, no-obligation strategy session where we'll audit your current campaigns (or help you map out your first ones) and give you actionable advice you can implement immediately. There's no hard sell, just straightforward, expert advice tailored to your SaaS business. Book your free consultation today.