Someone might suggest Ecosse, I would suggest not Ecosse at least til he gets more organised. Just a total comedy of errors for me though, did get the job done in the end in fairness and he does have a wild range of colours and options. Absolutely not Hendersons, my frame had blasting grit in the finish! “Totally normal with powdercoat mate”, literally fixed that situation by walking out with the frame without paying and being threatened with the police.
Anyway. I am taking some wheels and a trials frame to R&O in Bathgate as soon as I decide on the colour, they did some car wheels for me which came out great. He is really a “will coat anything metal” place and not a bike specialist so might not suit you.
Worth checking out Central Cosmetics in Stirling maybe?