Thanks for all the replies, sounds like its best to keep the bleed from the thermastat housing, I think I'm going to mount radiator on top of trayback with the header tank slightly above top of rad, run large bore pipes under car, plumb largest pipe from header tank to lowest point of top hose like it would be normally, then run a smaller hose from thermastat housing to the rad and y it into header as normal. Think this should solve bleed problems. I was hoping I could get away with not running bleed hose to back of car but sounds like its best to.
Alan