Short answer: The best plumbing websites do seven things. They put a phone number you can tap at the top, name every town covered, show proof you are registered, give each service its own page, show real jobs, show named reviews and make the enquiry form take a photo. A site missing two or three of these still looks fine. It just loses the customers who compare.
The panic call finds you whatever your site looks like. Someone with water through the ceiling rings the first number they see. The boiler replacement, the bathroom refit and the new heating system are different. Those customers open three tabs and pick one. This is what they check.
1. A number you can tap, at the top
On a phone, the call button is the site. If the number is in the footer, or is plain text that does not dial, you have added a step to the one action you want. Put it in the header and keep it there as the page scrolls.
2. The towns you actually cover
Searches like "plumber near me" and "plumbers in [town]" reward pages that name the place. A line saying "Plumbing across Leeds" is not enough. List the towns and districts you will really drive to. It also stops calls from forty miles away that you will turn down anyway.
3. Proof you are registered
If you work on gas appliances in the UK you must be on the Gas Safe Register, and customers are told to check the ID card. Show your registration number on the page. For unvented hot water or oil work, show the relevant qualification. A visitor who can check you in ten seconds ranks you above one who cannot.
4. A page for each service
"Boiler repair", "leaking pipes", "bathroom installation" and "power flushing" are separate searches. One page that lists them all competes for none of them. A short page each, with the price range if you can state one, gives Google a reason to show you and gives the customer an answer.
5. Photos of real jobs
A stock photo of a smiling man holding a wrench tells a visitor you have nothing of your own to show. Before-and-after photos from your own jobs, with the town and what was done, do more than any paragraph of wording. Never use an image you did not take.
6. Reviews from named customers
"Great service!" with no name reads as written by the plumber. A first name, a town and what was fixed reads as a person. Put each review next to the service it is about rather than in one block on the homepage.
7. An enquiry form that takes a photo
Ask for the same things you would on the phone: what is wrong, the property, a photo of the boiler or the leak, and a postcode. Small jobs can then be quoted from the message, and you know which parts to load before the van leaves.
What this costs if you skip them
None of these is hard. The cost of leaving them out is the planned work, the jobs worth having, going to whoever's site answered the question first. If you want all seven done for you, with no payment until you have seen the site live, our plumber website service is built around exactly this list, and the UK plumbers page has the pricing. If you are still working out what a site should cost, start with how much a website costs for a small UK business.