London: The Ultimate Guide To Vetting Paid Ads Experts

Finding a decent paid ads agency in London can feel like a proper nightmare. The market is absolutely flooded. You've got massive, faceless network agencies in the City, trendy Shoreditch outfits that are all style and no substance, and a million one-man-band 'gurus' promising the earth. Most of them are brilliant at selling themselves, but not so great at actually delivering a return for a business like yours. Tbh, it's a minefield.

The problem is that most business owners start in the wrong place. They look at slick websites, they get impressed by client logos, they listen to a confident sales pitch. But that's not how you find a real partner. You need a better process. You need to flip the script and make them prove their worth to you, not the other way around. This isn't about finding someone to just run your ads; it's about finding a partner who understands the commercial reality of your business and can make your ad spend work as a genuine investment, not an expense.

So, where do I even begin the search?

Before you even type "paid ads agency London" into Google, you need to stop. The first place to look isn't at an agency, it's inside your own business. The single most important piece of homework you can do is to understand your numbers. Specifically, what a customer is actually worth to you.

I've seen so many businesses come to us obsessed with a low Cost Per Lead (CPL), without any idea what they can actually afford to pay. They just want 'cheap leads'. But cheap leads are often just that: cheap. And worthless. A good agency will ask you about your numbers on the first call. If you don't know them, you're flying blind, and so are they. The key is to shift your mindset from "How low can my CPL go?" to "How high a CPL can I afford to acquire a great customer?".

The answer is in your Customer Lifetime Value (LTV). Once you know this, you know how much you can afford to spend to get a customer (your Customer Acquisition Cost, or CAC). A healthy business model usually aims for a 3:1 LTV to CAC ratio. So, if your LTV is £9,000, you can comfortably spend up to £3,000 to acquire that customer. This number changes everything. It turns advertising from a gamble into a calculated investment.

I've built a simple calculator below based on the formula we use. Play around with your own numbers. This is the foundation of any successful ad campaign.

How do I filter out the rubbish and find the real experts?

Once you know your numbers, you can start looking outwards. But you need a framework. You need a way to quickly decide who is worth your time. Forget their blog, their awards, their fancy office address. Focus on one thing: case studies.

But not just any case study. A picture of a client with a nice quote is useless. You need to see proof. Real, hard numbers. And ideally, for a business that looks a bit like yours. If you sell B2B software to finance firms in Canary Wharf, a case study about a fashion ecommerce brand in Manchester isn't all that relevant, is it? You need to see they have experience in your world.

Look for things like this:

• -> Did they increase revenue? By how much in pounds (£)?
• -> What was the Return on Ad Spend (ROAS)?
• -> Did they lower the Cost Per Acquisition (CPA)? From what to what?
• -> What platforms did they use? LinkedIn for B2B? Meta for eCom?
• -> Is the case study recent? The ad world changes fast.

I remember one B2B software client we worked with where we got their CPL on LinkedIn down to $22 for highly qualified decision makers. Another was a medical job-matching platform where we slashed their CPA from £100 down to just £7. Those are the kind of specific, tangible results that prove expertise. Vague promises don't. A good agency will have these case studies front and centre. If you have to dig for them, or if they're all fluff, it's a massive red flag. Move on. Their is simply no time to waste.

To make it simpler, here's a mental flowchart to follow. It'll save you hours of wasted time.

Okay, I've found one with good case studies. What happens on the first call?

This is where the rubber meets the road. This first interaction is absolutely critical, and it's where you can tell a true expert from a salesperson. Your goal for this call is not to be sold to. It's to get free advice. A genuinely confident and experienced agency isn't afraid to give away expertise. They know that by demonstrating their value, you're more likely to want to work with them.

We offer a free initial consultation where we actually get into a potential client's ad account and review their strategy with them. We'll point out what's working, what's not, and give them a few things they could do right away to improve things. This is the standard you should expect. If the call is just a PowerPoint presentation about how great they are, hang up.

Here are the red flags to listen for:

• Guarantees: "We'll definately get you a 5x ROAS in 3 months." This is the biggest lie in advertising. No one can guarantee results. The market is unpredictable. Anyone making promises is a charlatan.
• "Secret Sauce": "We have a proprietary method..." This is usually code for "We don't really have a process and we're hoping you don't ask." A real pro will happily talk about their process for testing, creative, and optimisation.
• They don't ask hard questions: If they don't ask about your LTV, your margins, your sales cycle, your ideal customer's biggest pain point... how can they possibly build a strategy for you? They're just planning to run generic ads.

And here are the green flags—the signs you might have found a winner:

• They challenge you: They might question your target audience, your offer, or your landing page. This is good. It shows they're thinking critically about your business, not just about your ad spend.
• They talk about YOUR business: The conversation is 80% about your challenges and goals, and 20% about them.
• You leave the call with an idea: You should walk away with at least one specific, actionable thing you could do to improve your marketing, whether you hire them or not.

What kind of results should I even expect in the UK market?

This is a fair question, but again, the answer is "it depends". It depends on your industry, your offer, your price point, and how competitive your niche is. Running ads for a home cleaning service in a small town is very different from running ads for a fintech SaaS product in London.

However, I can give you some ballpark figures based on the campaigns we've run for UK and other developed countries. This isn't a promise, but a realistic benchmark. For a simple conversion like a lead or a signup, you're often looking at a Cost Per Click (CPC) somewhere between £0.50 and £1.50. A decent landing page might convert 10-30% of that traffic. So, do the maths: your Cost Per Lead could be anywhere from £1.60 (£0.50 / 30%) to £15 (£1.50 / 10%).

For eCommerce, where the conversion is a sale, the numbers are different. Conversion rates are naturally lower, maybe 2-5%. So your Cost Per Purchase could be between £10 (£0.50 / 5%) and £75 (£1.50 / 2%). Of course, for eCommerce, what really matters is ROAS—the total revenue generated for every pound spent.

We've had some great successes for clients. A home cleaning company saw a cost of just £5 per lead. A women's apparel brand hit a 691% ROAS. But we also have clients in super competitive spaces, like an HVAC company, where leads cost closer to $60. The key is that they knew their LTV, so they knew a $60 lead was still highly profitable for them. The raw CPA or ROAS number is meaningless without the context of your business's economics.

What about asking for references? Should I talk to their clients?

Here's a contrarian view for you. Tbh, if a potential client asks us for references after they've seen our detailed case studies and we've given them an hour of our time in a free strategy review, it's an instant red flag for us. It signals a deep lack of trust right from the start. A relationship that begins with suspicion is unlikely to become a successful partnership.

Think about it. An agency will only ever give you the contact details of their happiest clients. You're never going to get an unbiased view. The real proof is in the work. The case studies are the evidence. The strategy call is the interview. If you're not convinced after those two things, then they are not the right fit for you. Trust your gut. A good partnership has to be built on mutual trust and respect for each other's expertise. If you feel you need to 'check up' on them, the trust is already broken.

This is the main advice I have for you:

Navigating the London agency scene is tough, but it's not impossible if you have a clear process. To sum it all up, here is the exact framework you should follow.

So is it worth hiring an expert?

You could try to do all this yourself. You could spend months learning the intricacies of Google Ads, Meta's algorithm, and LinkedIn targeting. You could waste thousands of pounds on ads that don't work, testing audiences and creative. Or, you could partner with someone who has already made all those mistakes and knows how to get it right, faster.

Hiring the right agency isn't an expense. It's an investment in speed and expertise. It's about getting a strategic partner who is as focused on your business's bottom line as you are. They can help you avoid the costly pitfalls, navigate the complexity of the ad platforms, and build a scalable, profitable growth engine for your business in a ferociously competitive market like London.

It's a big decision, and it pays to get it right. If you've gone through the steps above and you're still not sure, or you just want a second opinion on your current strategy from someone who lives and breathes this stuff every day, then it might be time to talk to a professional.

If you'd like a no-nonsense, no-obligation review of your advertising strategy, we offer a free consultation where we'll give you our honest assessment and some actionable advice. It's a chance to see how a true expert partner would approach your business, without any pressure.