My hydro dipped parts look as good now as the day I fitted them (I'm careful with keys in my hand mind & don't wear rings).
Basically they prep your part, spray it with a primer & base coat of paint, dip it in a water filled tank with your chosen pattern on a sheet that when it's sprayed with an activator liquefies, then once it's dried they use a clear lacquer over the part to protect the finish.
Bound to be a company local to you that will do it or you can usually post the parts for dipping at various companies around the UK. A local company called AquaGraphix did mine. They're a forum trader on here now too.
Link: http://www.350z-uk.com/forum/227-aquagraphix/