Competition for commercial searches in London is dense, and cost per click in the capital tends to run above the national average for the same keywords. A budget set by instinct, such as "£1,500 a month and see what happens", usually runs out before the data says anything useful.

Starting from margins gives every click a ceiling, and the ceiling tells you which keywords are viable.

Work out what a click is worth

Take the gross profit on an average customer, divide it by the number of leads you need to win one, then multiply by your landing page conversion rate. The result is the most you can pay per click before the campaign loses money.

Here is an illustration. A service earns £1,200 gross profit per customer, the team wins one in five leads, and the page turns 8% of visitors into leads. £1,200 divided by five is £240 per lead, and 8% of £240 is £19.20 per click, so a keyword costing £25 a click loses money at those rates.

This shows why improving the conversion rate or close rate often creates more room than bidding higher. Moving the page from 8% to 10% lifts the ceiling to £24 with no change to the ad.

Set the budget from the learning you need

A new campaign needs enough conversions to show a pattern. If your target cost per lead is £60, thirty leads cost £1,800, and a budget well below that over two months leaves you guessing.

Decide how many conversions you need before judging the campaign, multiply by your target cost, and treat the result as the minimum test budget.

Tighten London targeting

•     Choose the "presence" location option, so people who merely searched about London are excluded from the audience

•     Target the boroughs or postcode districts where customers live when your service has a travel radius, and skip Greater London as a whole

•     Add bid adjustments for areas that convert better once you have a month of data

•     Schedule ads for the hours when phones are answered, since a call at 9pm to an empty office wastes the click

Review the search terms report weekly for the first two months. Add negative keywords for terms like jobs, free, DIY, training and cheap if they do not suit your offer.

Be careful with automated campaign types

Performance Max and broad match can find new customers, and they can also spend quickly on irrelevant traffic. Start with tightly themed search campaigns where you control the keywords, bring in broader types once the account has conversion history, and set brand exclusions if you want new customers measured separately.

Fix the landing page before raising spend

A click costing £20 that lands on a general homepage wastes money. Send each ad group to a page that repeats the search intent in its headline, shows the phone number and form without scrolling, and loads quickly on mobile.

Many London searches happen on phones between meetings and journeys, so test the page on a mid-range handset over mobile data and not only on office wifi.

A first-month plan

•     Week one: set up conversion tracking for forms, calls and bookings, then test each one with a real submission

•     Week two: launch two or three tightly themed ad groups, each with at least three ad variants

•     Week three: read the search terms report, add negatives, and pause ads that attract the wrong audience

•     Week four: move budget toward the ad groups producing qualified leads and note what you learned for month two

Track phone calls properly

Many London service enquiries arrive by phone. Use call tracking that counts a call as a conversion only after a minimum length, such as 60 seconds, and ask callers how they found you so you can check the data against what people say.

Judge the numbers fairly

Early cost per lead figures are noisy, so avoid changing bids every day. Wait until each ad group has collected enough clicks to show a pattern before cutting or scaling it.

Allow for seasonality too. Many B2B accounts see quieter periods in August and around the end of December, and a dip in those weeks says more about the calendar than the campaign.

When a specialist helps

Account structure, conversion tracking and ad testing take time to set up properly. A PPC and paid media agency can audit an existing account in a few days, and the audit alone often shows where money leaks: loose match types, missing negatives, or conversions that count page views. Ask for the findings in writing so you can act on them in house if you choose.