Ever since I have had the car there has been a rattle in the clutch area when in neutral or under load. This is a known design fault of the home-made thrust bearing, but there is was also a rattle from the clutch fork itself (The part the cable pulls onto to release the clutch). A bit of research showed that the original fit of the clutch and MT75 gearbox to the Ford Escort/Sierra actually came with a tensioning spring between the clutch fork and the bell housing so it would not rattle. This had not been fitted to the car so it seemed logical to fit one.
This is what it looks like on a diagram. I already have the copper water pipe installed to make the clutch adjustment correct, so now I have just added a spring to hold the clutch under tension. It's a very weak spring so there is no risk of burning out the clutch.
And here is the spring wired into position.
It remains to be seen if this reduces the rattle.