Companies that I have used and wouldn't hesitate to use again and recommend:
Reloading Solutions, need little introduction.
South Yorkshire Shooting Supplies, need I say more!
Steve Beatty at Ivythorn Sporting in Somerset, great customer service and back up, a pleasure to deal with.
Chris Potter Fieldsports in Tunbridge Wells Kent, bought and sold a few rifles over the years here. Great all round gunshop and friendly staff.
Eastern Sporting in Essex, whilst rifles aren't his speciality, Alan will bend over backwards to help you out, great prices and customer service.
Roding Armoury, Essex good source of bullets and powders.
Also Midway UK, never had a problem with them personally, Riflecraft,