IT'S ALIIIIIVE!!!!! We had another go last night, and spotted something really silly.
When everything is in the timed up position, it wouldn't fire, so we rotated the crank by hand through 1 revolution, which effectively puts the cam and fuel pump 180 deg out from the crank. after scratching our heads for a few minutes while we looked at the partially assembled bottom end on the engine stand, and thought of something.....
So, we left the timing set with the crank at TDC on 1 & 4, the cam effectively 180 deg out, and set the pump to it's timed position - and it fired and ran!!!!
Weird or what? none of the pulley's were disturbed when i changed the belt, it was a case of old belt off, new belt on, tighten tensioner, rotate engine couple of times to make sure it lines back up, job done.
Cheers to all for the pointers, it gave us somewhere to look.