Cheers for the replies guys.

Yeah, the car has had a cambelt change at the same point, but has been timed up as per the ford workshop manual, and checked by 3 separate people as i was shitting it, thinking that I'd do it wrong. - Its just odd that sometimes it will run fine, but othertimes it wont!

Once i'm back from LeMans (the cos isn't going as I don't want to risk it...)
I'll whip everything off of the front of the car again, and check the CPS / pulley allignment, and re-check timing etc again...

I'll also check the engine earth strap, as it seemed to be secure, but you never know..
Stu - I'll be in touch and re-book that set-up once its running semi-normally

Cheers