London's Guide to Vetting Ad Spend Experts

I get it. You're based in London, probably one of the most competitive markets on the planet, and you're pumping money into ads with the nagging feeling that most of it is disappearing into a black hole. You know you need an expert, a proper ad spend consultant, but the market is saturated with agencies in Shoreditch and freelancers in Soho all promising the earth and delivering a pile of useless jargon-filled reports. The inefficiency is costing you, not just in wasted budget, but in lost opportunity.

The truth is, most businesses hire the wrong person. They look for a media buyer, a campaign manager, a "consultant." What they actually need is a growth partner who is obsessed with their business model, their customers' deepest pains, and, most importantly, their profit margins. Before you interview another soul, you need to change the entire framework you're using to vet them. This guide will show you how to do it, how to spot the pretenders, and how to find someone who can actually deliver a demonstrable return on your investment.

So, you think you know your customer?

Let's be brutally honest. When I ask a potential client in London who their ideal customer is, I usually get a response like: "We're targeting finance companies in the City with 50-200 employees." That's not a customer profile; it's a sterile, useless demographic. It tells you absolutely nothing about how to actually sell to them, and it's why your current ads are probably being ignored.

To stop burning cash, you have to define your customer not by who they are, but by the specific, urgent, and expensive nightmare that keeps them awake at night. Your Ideal Customer Profile (ICP) isn't a person; it's a problem state. A career-threatening problem.

Think about it. The Head of Sales at that finance firm isn't just a job title. She's a leader terrified of missing her quarterly target because her team is buried in manual data entry instead of closing deals. The problem isn't 'needing a CRM'; the nightmare is 'reporting to the board that they've missed their numbers again, putting her own job on the line.' Your product or service doesn't sell features; it sells the solution to that nightmare.

I remember one B2B software client we worked with was selling a data enrichment tool. They were targeting "sales managers." It wasn't working. We helped them redefine their ICP's nightmare: 'The soul-crushing moment a sales rep spends hours researching a lead, only to find the contact info is outdated, wasting a perfect opportunity.' We changed the ad copy to speak directly to that frustration. The result? Their cost per lead dropped to just $22 on LinkedIn Ads, because we were finally talking to the right people about the right problem.

Before you even think about hiring a consultant, you need to do this work. Map out the nightmare. What is the tangible cost of inaction for your customer? What's the emotional toll? Once you know this, you've got the blueprint for your entire marketing strategy. And you'll be able to spot a good consultant from a bad one instantly, because a good one will ask you about this on the very first call. A bad one will ask about your budget.

What's the one number that actually matters?

Forget ROAS for a second. Forget Cost Per Click. Forget all the vanity metrics agencies love to put in their monthly reports to make themselves look busy. There is only one equation that truly dictates whether your ad spend is an investment or an expense: the ratio between your Customer Lifetime Value (LTV) and your Customer Acquisition Cost (CAC).

The real question isn't "How low can my Cost Per Lead go?" but rather "How high a CPL can I afford to acquire a fantastic customer?" Calculating your LTV is the first step to answering that. Most founders I speak to in London have a vague idea, but they've never actually done the maths. Let's fix that.

Here’s the simple formula:

LTV = (Average Revenue Per Account (ARPA) * Gross Margin %) / Monthly Churn Rate %

Let's take a hypothetical London-based SaaS company.

• Their ARPA is £400/month.
• Their gross margin is 75% (after server costs, support, etc.).
• They lose about 5% of their customers each month (their churn rate).

The calculation would be: (£400 * 0.75) / 0.05 = £300 / 0.05 = £6,000.

Each customer is worth £6,000 in gross margin over their lifetime. Now you have the truth. A healthy business model aims for an LTV:CAC ratio of at least 3:1. This means you can afford to spend up to £2,000 to acquire a single new customer. If your sales team converts 1 in 10 qualified leads, you can afford to pay up to £200 per qualified lead. Suddenly, that £150 lead from Google Ads doesn't seem so expensive anymore, does it? It looks like a bargain.

This is the maths that unlocks aggressive, intelligent growth. Use the calculator below to find your own LTV. It will change how you view your ad spend forever.

How to spot the time-wasters from a mile away

Now that you're armed with your customer's nightmare and your LTV, you're ready to start vetting consultants. The London agency scene is a minefield of over-promising and under-delivering. Here’s how to quickly filter out the 90% who will waste your time and money.

The first red flag is anyone who promises specific results. "We'll get you a 5x ROAS in 90 days." It's impossible. Tbh in paid advertising, you can't really promise anything. There are too many variables. A real expert talks in terms of process, strategy, and testing methodologies, not guaranteed outcomes. They'll talk about benchmarks from similar clients, but they'll never make a solid promise.

The second is a fixation on their own proprietary "system" or "secret formula." It's usually just a fancy name for a very standard process. True expertise isn't a black box; it's a transparent, logical approach to problem-solving. They should be able to explain their entire strategy to you in plain English, without relying on buzzwords.

Third, look at their case studies. Are they vague and full of vanity metrics like "impressions" and "reach"? Or do they talk about real business outcomes, like revenue generated, CPL reduction, and LTV:CAC ratios? We have detailed case studies for our clients that walk through the full strategy, from the initial problem to the final, profitable result. For one eCommerce client selling cleaning products, we didn't just increase their revenue by 190%; we achieved a 633% return on their ad spend on Meta Ads. That's a real result, not fluff. Anyone you consider hiring should have several examples just like that, ideally in a similar niche to yours. If they dont, its probably not a good fit.

Finally, the most arrogant and telling red flag of all: the "Request a Demo" button as their primary call to action. This is high-friction and low-value. It presumes you have nothing better to do than sit through a sales pitch. A confident expert, a true consultant, will do the opposite. They will offer to provide immense value upfront, for free, to prove their worth. This is often a free, in-depth audit of your existing ad accounts. It’s their chance to show you, not just tell you, that they know what they're doing. This is so critical that we've made it a core part of our own process, offering a free initial consultation to review strategy and accounts. It's the ultimate 'try before you buy'. If an agency isn't willing to do this, they're either not confident enough in their skills or they're too focused on their sales process instead of yours.

Use this flowchart to guide your initial vetting process. It'll save you hours of wasted meetings.

The only questions you need to ask on an intro call

Once you’ve found a consultant that passes the initial sniff test, you'll get on a call. This is where you separate the true experts from the smooth-talking salespeople. Most business owners ask the wrong questions, like "What's your fee structure?" or "What ROAS can you get me?". Don't do that. Instead, your goal is to probe their strategic thinking and real-world experience. Here are the questions that matter:

1. "Based on what you know about my business, what is the single biggest opportunity you see, and what is the biggest risk?"
This question forces them to think on their feet and apply their expertise directly to your situation. A salesperson will give a generic answer about "optimising campaigns." An expert will point to a specific weakness in your funnel, a missed targeting opportunity on LinkedIn, or a flaw in your offer, and then explain the commercial implications of both fixing it and ignoring it.

2. "Walk me through a campaign you ran for a client like me that failed. What went wrong and what did you learn?"
This is my favourite. Everyone loves to talk about their wins. Only confident, experienced practitioners are comfortable discussing their failures. It shows humility, honesty, and most importantly, a commitment to learning and iteration. If they claim they've never had a campaign fail, they're either lying or they haven't managed enough campaigns to be a real expert. Their answer will reveal their problem-solving process under pressure.

3. "If we were to work together, what would you need from me and my team in the first 30 days to be successful?"
This question shifts the focus from what they will *do* to what they will *need*. A great consultant understands that success is a partnership. They'll ask for access to your analytics, customer data, sales team feedback, and subject matter experts. They'll talk about setting up tracking and reporting. A poor consultant will say something like, "Just give us the budget and we'll handle the rest." That's a recipe for disaster and shows a lack of understanding of how integrated marketing truly works.

4. "How do you approach the balance between prospecting for new customers and retargeting warm audiences?"
This is a more technical question that tests their understanding of full-funnel marketing. Their answer should be nuanced. They should talk about budget allocation based on business goals (e.g., aggressive growth vs. profitability), the different messaging required for each stage, and how they measure success differently for top-of-funnel and bottom-of-funnel campaigns. If they give a one-size-fits-all answer, they lack strategic depth.

Listen carefully to their answers. Are they thoughtful and specific, or are they full of vague platitudes? The quality of their questions back to you is just as important. A real expert will grill you on your LTV, your sales cycle, your customer feedback, and your business goals. They're trying to qualify *you* as a client just as much as you're qualifying them. It should feel less like a sales pitch and more like a high-level strategy session. If it does, you might have just found your expert. And if you're ever in doubt, a comprehensive guide to vetting consultants can give you an even more detailed framework.

Case studies are proof, everything else is just talk

At the end of the day, the single most powerful piece of evidence a consultant can provide is a portfolio of successful case studies. Not just testimonials, but detailed breakdowns of real campaigns for real clients, showing the problem, the strategy, and the quantifiable results. When you're assessing a potential London-based consultant, you should demand to see these. And you should look for relevance – have they worked with businesses of a similar size, in a similar industry, facing similar challenges?

For example, if you're a SaaS founder, a case study about a local plumbing company is pretty much irrelevant. You'd want to see something like the work we did for a medical job matching SaaS platform. Their Cost Per User Acquisition was a painful £100. By restructuring their Google and Meta Ads campaigns and refining their targeting, we brought that down to just £7. That's a 93% reduction and a transformative result for their business. We also worked with another B2B software client and generated 4,622 registrations at just $2.38 each using Meta ads, proving you can get high-quality B2B leads from platforms other than LinkedIn.

If you're in eCommerce, you'd want to see proof of driving direct sales and a positive return. For a women's apparel brand we worked with, we generated a 691% return on ad spend using a mix of Meta and Pinterest Ads. For a subscription box company, we hit a 1000% ROAS on Meta. These aren't just good results; they demonstrate a deep understanding of different platforms and how to make them work for specific business models.

The numbers in these case studies tell a story. They show an ability to not just spend a budget, but to turn that budget into a multiple of itself in revenue. This is what "demonstrably improving ROI" actually looks like in practice. It's not about vague promises; it's about a track record of performance. The chart below shows the kind of ROAS figures you should be looking for in a consultant's case studies. If their examples don't look anything like this, you have to question whether they have the experience to deliver the results you need.

Finding the right consultant is a critical business decision, and it requires more diligence than just a quick Google search for "ad agency London". You need a structured approach to filter out the noise and identify true experts who can become strategic partners in your growth. Getting this hire right is often the difference between stagnation and scalable success, so it's worth putting in the effort. For a deeper look at what to expect, check out our framework for finding an expert London advertising consultant.

Your actionable plan for finding the right expert

We've covered a lot of ground, from redefining your customer to calculating your LTV and spotting agency red flags. Now, let's pull it all together into a clear, actionable plan. This is the exact process you should follow to find a reliable ad spend consultant in London who can actually improve your ROI.

This isn't about finding someone to just manage your ads; it's about finding a partner who can help you build a more profitable business. It requires you to do some homework first, but this preparation will pay dividends by ensuring you hire the right person and avoid costly mistakes. Remember, the goal is to fix your paid ads ROI for good, not just apply a temporary patch.

I've detailed the main recommendations for you below in a summary table. Think of this as your checklist for the entire process.

It's time to stop wasting money

Finding the right ad spend consultant in a city like London is a daunting task, but it’s not impossible if you approach it with the right framework. By focusing on your own business fundamentals first—your customer’s real problems and your unit economics—you change the entire dynamic. You're no longer just buying a service; you're seeking a strategic partner who can help you solve valuable problems at a profit.

Stop rewarding agencies that hide behind jargon and vanity metrics. Demand transparency, demand a focus on business results, and demand proof of past performance. The best consultants will welcome this level of scrutiny because it separates them from the competition. They aren't afraid to open up their process, discuss their failures, and provide immense value upfront because they are confident in the results they can deliver.

Executing a world-class paid advertising strategy that genuinely moves the needle on revenue requires deep expertise, constant testing, and a strategic mindset. It's a full-time job that most founders and marketing managers simply don't have the bandwidth for. While this guide gives you the tools to find the right expert, partnering with one can accelerate your growth exponentially by avoiding costly trial-and-error and implementing proven strategies from day one.

If you’re tired of the guesswork and want to have a direct conversation about how these principles can be applied to your business, consider scheduling a free, no-obligation strategy session. We can audit your current ad accounts, identify the biggest opportunities for growth, and give you a clear, actionable plan. It's the first step to turning your ad spend from a source of frustration into your most powerful engine for growth.