Hi Paul,
The motor im using is a brand spanking Lucas one. I replaced the original thinking that it was the cause of the clunk as the 140 gearwheel seemed to be a loose fit in the brass bush in the body of the motor.
What i have noticed is that the original gearwheel is a nice tight-ish fit in this bush, whereas the 140 gearwheel just slides in and out.
Edit: Maybe im being too picky and i wont hear it when engine running etc, but there is definately a difference between the gears as when i had the original 200tdi style one in, it was near silent.