Blimey that took a while, and I still can't find the superdooper website that listed all of them
Anyway, from memory some of the bigger names are Potton and Scotframe. Then there are rafts of nice companies that will design you a timber frame to your specification, rather than as a full kit. You might find more information on www.selfbuildabc.co.uk or www.ebuild.co.uk. Otherwise, googling oak frame buildings/timerb frame manufacturers/kit houses seems to turn up a lot of results.
Sorry - time limited at the moment but will try and resurrect my searches later!