I am not sure any of the UK suppliers are still in business. Looks like Roland of B4 left last year (looking at his Linkedin profile) and the other vendor, name escapes me at the moment, went out of the CRT business even before that.
Though Curt Palme is not located in the UK he ships there and is a very well thought of in the CRT community. I have dealt with him the past on parts and have no complaints. You can find him here: http://www.curtpalme.com/
The cheapest solution is to find a whole projector which is what I have mostly done but as these things get older the change of a problem in them goes up so their is no guarantee the parts will all be working whereas Curt tests and provides a warranty on his parts.