If he is convenient to you, Steve Kershaw does very good work, he is up near Hull I think.
Chop, thread and recrown job is about £125.
Think very seriously about a lightweight muzzle can, Roedale is excellent (230 grammes), ASE also have a new light can, can't remember the name, but it weighs in around 250 grammes.
You sure you don't mean ATEC rather than ASE?
Aluminum CMM4 250gr.
why do muzzle mounted moderator (as opposed to over barrel) prove less troublesome?A reputable gunsmith, definitely. Improperly fitted moderators can cause all sorts of difficult-to-diagnose problems with accuracy. Muzzle cans (ie. not over -barrel) like the Jet-Z or the ASE Utra S5 avoid a number of these problems but they still need to be fitted by a good gunsmith.