I can highly recommend Perth Powder Coating at Almondbank - just outside Perth. Tel:- 01738 583270 and ask for Brian who owns the company.
He's refurbished and repainted the alloys on my old car, the wifes car, a friends car and he's just about to get the set that's on my Scooby. Absolutely fantastic work.
He charges £40 per wheel regardless of whether they're bare, with tyres on, or still on the car.