Kontra - there is a company in Stockton that is very highly regarded in stuff like this.
They are called Romax - had all four of my alloys on the old 8L S3 done when I first bought it (was 2nd hand!) and they did a cracking job with a perfect finish.
They've also just repaired one of my dads alloys (he says the curb jumped out at him!!)
Might be worth a look.
SEM in Sunderland are excellent too, bit cheaper than Romax if I remember...