Hi, there was a series of articles on refurbishing britania lathes in the model engineer in the late seventies/early eighties that I can remember reading. your local library may be able to get copies as they keep bound volumes within the library service.
you could at one time still get replacement parts from the trade in birmingham but I think the company went into liquidation in the late nineties, but a call to the model engineer editor may prove useful.
regards
mike g