Am looking for a firm that can remove some brake bosses and powdercoat a frame. Any suggestions?

hack saw, grinder, emery paper!!!

or go to a car body shop.

Most frame builders.
Argos have done good frame repair/respray jobs for me in the past.

£15 angle grinder from screwfix, a cutting disc and a sanding disc will do the trick, keep cooling it with a wet rag as you do it to stop the frame work hardening and then sand the area down afterwards.

Where are you based?

Need any bearings done at the same time? Guy on here'll give it a 10% performance increase!

Might be worth chatting with 18 Bikes if you're up this way? They talked with me a while back about doing a similar frame prep (boss removal) before sending it off to their powder coater for the finish – not exactly a one-stop-shop but I suspect they'd do a proper job of it.

braze them off don't use a grinder

Bobjacksoncycles.

DIY removal faw shoooer

Thanks guys, i've just sent argos a mail.

Mercian Cycles in Derby
Primarily road and touring bike manufacturers (and have been longer than Raleigh) but do good job on repairs, resprays and stuff like that on all bikes
Decent prices too