I need a frame for a yamaha xj750 seca, does anyone have a good one in uk, or can i use say a xj650 frame?

no,the xj650 is a different frame,try any bike breakers,how about eds in nottingham?,he also advertises on ebay,i recently red an article about his breakers,involving 10 furniture lorry loads of parts.i think he'd be a good starting point