A shop has an address customers walk into. A builder has a van and a list of towns, and Google treats the two differently. A builder's Google Business Profile is a service-area business: the address is hidden, the pin is not on your house, and the profile carries a service area, the towns you take jobs in. The map pack for “extension builders” with a town is decided by that service area, the reviews, and the primary category, more than by the website.
So when we say one builder per town, the town is the one on your profile, plus the service area around it that we agree with you in writing in the audit reply. Not a postcode district, not a thirty-mile circle you would like to cover, and not a county. A real town and the places you actually drive to from it. That is what the tier protects, and it is written down before you pay anything, so there is nothing to argue about later.
The work itself is the same everywhere. The pages are written after a call with you, the profile is set up from your own account, and the reviews come from your customers. None of it needs us on site, which is why a builder in Cornwall and a builder in Cumbria get the same service from the same person in Wrexham. What changes from town to town is the competition, and the audit says how long a town is likely to take rather than charging more for it.