TLDR;
- Stop looking at flashy client logos. The only thing that matters is if they have specific, detailed case studies for UK B2B SaaS companies with results in pounds (£), showing cost per trial or demo, not just clicks.
- The initial "free consultation" or "audit" is the real interview. If they spend the whole time selling instead of providing genuine, actionable advice on your account, they're not the right partner. A good one will give you value for free.
- Before you talk to anyone, you MUST define your ideal customer's career-threatening nightmare. A good agency will build your entire Google Ads strategy around solving this pain. A bad one will just ask for a list of keywords.
- This article includes a fully interactive LTV to CAC calculator. Use it to figure out exactly what you can afford to pay for a customer and a lead, so you can call out agencies on unrealistic CPL targets.
- Forget the idea that the best agencies are in huge offices in Shoreditch. The best partner is the one who demonstrates a deep understanding of the UK tech scene, SaaS unit economics, and how to turn ad spend into predictable revenue.
As a B2B SaaS founder in London, trying to find a Google Ads partner that actually knows what they're doing is a proper nightmare. Every agency website is full of jargon and vague promises. They all claim to be "data-driven" and show off logos of companies you've heard of, but that tells you nothing about whether they can actually grow *your* business.
The truth is, most founders go about it all wrong. You're asking the wrong questions, looking at the wrong metrics, and are primed to get taken for a ride by a generalist agency that will happily burn your cash on campaigns that look busy but deliver zero pipeline. They'll treat your SaaS business like they would an e-commerce store or a local plumber, and that's a recipe for disaster. The problem is that finding a good partner in the city can be tough, which is why we put together this guide on how to vet London ad agencies.
So, how do you spot the real experts in the sea of pretenders?
First thing, you need to completely change how you look at their track record. Forget vanity metrics. I don't care if an agency got a million impressions for a client. It's meaningless. I also don't really care about their swanky client list unless those clients are very similar to you.
Your number one filter should be: show me the B2B SaaS case studies. And not just any case studies. I'm talking about UK-based SaaS companies. I want to see results in pounds, not dollars. I need to see that they understand the nuances of the UK market. For a SaaS business, success isn't measured in Return on Ad Spend (ROAS) in the first month. The sales cycle is longer. The real metrics are things like Cost Per Trial, Cost Per Demo, and ultimately, Customer Acquisition Cost (CAC) against Lifetime Value (LTV).
For instance, I remember one software client where we used Google Ads to acquire 3,543 users at just £0.96 per user. In another campaign for a medical job matching SaaS, we reduced their Cost Per Acquisition from a painful £100 down to just £7. That's the sort of specific, tangible result you should be looking for. If an agency can't show you this kind of track record with businesses like yours, they're not the right fit. It's that simple. Finding the right partner is tough but our guide on finding a London SaaS marketing agency might help.
Why you need to understand your customer's pain first
Here's a contrarian thought for you: you have no business talking to a Google Ads agency until you've done your own homework. And I don't mean keyword research. You need to get obsessively clear on your Ideal Customer Profile (ICP). But not in the way most marketers think about it.
Forget the sterile, demographic-based profile. "Companies in the finance sector in Canary Wharf with 50-200 employees" tells you nothing of value. It leads to generic ads that speak to no one. To stop burning cash, you must define your customer by their *pain*. Their specific, urgent, expensive, career-threatening nightmare.
Your Head of Engineering client isn't just a job title; she's a leader terrified of her best developers quitting out of frustration with a broken workflow. Your prospect in a legal tech firm isn't just 'needing document management'; their nightmare is 'a partner missing a critical filing deadline and exposing the firm to a malpractice suit.' Your ICP isn't a person; it's a problem state.
When you get on a call with a potential partner, a great one will dig into this. A bad one will just ask "so what keywords do you want to target?". You need a partner who can translate that customer nightmare into a full-funnel strategy. This is the difference between hiring a technician and a genuine growth partner.
Do you know how much a new customer is actually worth?
This is the next big question. The real question isn't "How low can my CPL go?" but "How high a CPL can I afford to acquire a truly great customer?" The answer lies in its counterpart: Lifetime Value (LTV). Most founders I speak to have a vague idea, but they haven't done the maths. Without this, you're flying blind, and you can't properly judge an agency's proposed strategy or performance.
A good agency partner, especially one that claims to be a specialist B2B ad consultant, should be asking you about these numbers on the first call. They need this to build a strategy that's actually profitable.
Here's the basic calculation:
LTV = (Average Revenue Per Account (ARPA) * Gross Margin %) / Monthly Churn Rate
Let's say your ARPA is £500, your gross margin is 80%, and your monthly churn is 4%.
LTV = (£500 * 0.80) / 0.04
LTV = £400 / 0.04 = £10,000
In this example, each customer is worth £10,000 in gross margin to your business. A healthy LTV:CAC (Customer Acquisition Cost) ratio is often cited as 3:1, which means you can afford to spend up to £3,333 to acquire a single customer. If your sales process converts 1 in 10 qualified demos into a customer, you can afford to pay up to £333 per demo. Suddenly, that £200 lead from Google Ads doesn't seem so expensive, does it? It looks like a bargain. This is the maths that unlocks intelligent, aggressive growth.
Use the calculator below to get a clearer picture of your own numbers. Play around with the sliders to see how small changes in churn or revenue can dramatically impact what you can afford to spend on ads.
What to look for in the initial consultation call
Okay, you've found a few agencies with relevant UK SaaS case studies. You've defined your customer's nightmare and you know your LTV. Now you book the calls. That free initial consultation is everything. This is where you separate the experts from the salespeople.
A bad agency will spend 30 minutes showing you a generic PowerPoint deck about their "process" and then ask for your credit card details. An expert will spend 90% of the time asking you sharp, insightful questions about your business and then give you actual ideas you can use, whether you hire them or not.
Here are some killer questions to ask them:
- -> Based on our ICP's nightmare that I've described, what are the top 3 high-intent keyword themes you would build our initial B2B SaaS Google Ads campaigns around? (This tests their ability to think strategically beyond the obvious).
- -> Talk me through your process for landing page and ad copy testing. How quickly do you expect to iterate? (This tests if they have a real system for optimisation).
- -> Tell me about a UK SaaS campaign you ran that *failed* at first. What went wrong, and what specifc steps did you take to turn it around? (This tests for honesty and problem-solving skills. Everyone has campaigns that fail; the good ones learn from them).
- -> Given our LTV is roughly £10,000, what would you aim for as a target cost-per-qualified-demo in the first 90 days, and how would you get there? (This forces them to apply their knowledge to your numbers).
The answers to these questions will tell you everything. Look for depth. Look for them pushing back on your assumptions. Look for someone who sounds more like a strategic partner than someone desperate to close a deal. That's how you'll know you've found the right fit.
- Guarantees specific results (e.g., "we'll double your leads in 30 days"). Tbh, that's impossible to promise.
- Focuses on vanity metrics like clicks, impressions, or CTR in their reporting.
- Spends the whole audit call talking about themselves and their generic 'process'.
- Uses a one-size-fits-all strategy without asking deep questions about your business.
- Is hesitant to show you specific UK SaaS case studies with real metrics.
- Is realistic and manages expectations about timelines and results.
- Talks about business metrics: Cost per Demo, LTV:CAC ratio, and sales pipeline contribution.
- Asks more questions than you do. They're trying to diagnose, not sell.
- Provides genuine, actionable advice and ideas you can use immediately.
- Gladly shares detailed case studies that are directly relevant to your business model.
What's the best approach then?
Choosing the right Google Ads partner is one of the most important marketing decisions a SaaS founder can make. Get it right, and you unlock a predictable engine for growth. Get it wrong, and you'll waste six months and tens of thousands of pounds with nothing to show for it but a bigger hole in your runway. It's often a difficult choice whether to go with a B2B ad management agency or freelancer.
The key is to stop thinking like you're just buying a service and start thinking like you're hiring a strategic partner. They need to understand your business, your customer, and your numbers on a deep level. The frameworks and questions in this guide are designed to help you cut through the noise and identify the small handful of agencies in London that actually have the expertise you need.
I've detailed my main recommendations for you below:
| Phase | Actionable Step | Why It's Critical |
|---|---|---|
| 1. Internal Preparation | Map out your ICP's "nightmare" scenario. Use the LTV:CAC calculator to understand your unit economics and determine a realistic target acquisition cost. | This arms you with the necessary strategic context. You'll be able to spot agencies that don't understand your business model from a mile away. |
| 2. Agency Research | Scour their websites for specific, detailed B2B SaaS case studies, ideally from the UK. Ignore any agency that can't provide them. | This is the single most effective filter. Past performance in a near-identical scenario is the best predictor of future success. |
| 3. The Audit Call | Treat it as an interview where *they* must prove their value. Ask the "killer questions" about strategy, process, and past failures. | You're assessing their strategic thinking and problem-solving skills, not their sales pitch. A great partner provides value for free. |
| 4. The Decision | Choose the partner who demonstrated the deepest understanding of your business and offered the most compelling strategic insights, not necessarily the one with the lowest price. | You're investing in a growth partnership, not buying a commodity. The right expertise will pay for itself many times over. |
Doing this properly takes time and effort, but the payoff is enormous. If you can find a true partner who can help you translate your customer's pain into profitable ad campaigns, you'll have a massive advantage over competitors who are still burning cash with generalist agencies.
If you're going through this process and want a second opinion, or want to see what a deep-dive strategy session looks like, we offer a completely free, no-obligation consultation. We'll audit your existing efforts (if any) and give you a straightforward, actionable plan. It's a chance to experience firsthand the level of strategic depth you should be demanding from any potential partner.
