A real page for each town, not a find-and-replace
Every city page gets its own headline, its own description of what the work looks like there, and the trades or industries you actually serve in that area. This matters more than it sounds. Google has a name for twenty near-identical pages with the city name swapped out, it calls them doorway pages, and it demotes them on purpose. Pages that differ only by one word are worse than having no city pages at all.