Lee, i think you might find that Steve Kershaw is based in or around Goole, down the M62, at least he was when he screwcut and fitted a mod for me 6 years ago.
Try `Browns lock stock and Barrel` in Hillsborough, Sheffield. He is my local gundealer who uses a gunsmith called Pat who i think is based around the Manchester area but picks guns up from Browns to repair etc. He has done a couple of screwcuts for me and done a good job and was about £50, but that may have changed slightly now as well as taking them to Brum for proofing. His number is 01142346222.
wadas