Welcome - the specialist shop in the Area is Mercian in Derby - not cheap though. No other specialist bike sprayers as such in Nottingham itself. There's a few powder coaters as to be expected - all depends on what your re-spraying, the $ you want to spend etc. You could try one of the local car garages who do re-spray work....that'll be my next port of call for some stuff that doesn't warrant huge investment.
