In reply to Removed User:
If you just want a single colour powdercoat (and are London based) then Armourtex in Hackney are good. They've done several frames for me all turned out beautifully - and the finish is pretty bombproof unlike paint resprays.
If you want a particular design or something like lugwork, then they're not the right sort of place - you want someone like Argos or Bob Jackson as some of the others have recommended. But they will be a fair bit pricier.