Thanks for your reply.
Cylinder head was leaking oil 4,000 miles ago, so the whole top half was replaced. Since then have had no problem until the car overheated a few weeks ago. There is no sign of oil in the foam or water coming out of radiator. Garage that has worked on my previous cars, and who replaced head gasket etc. are the ones who took car away and said it was dead so did not perform any tests, but I have driven it short distances since and it has overheated. If they had diagnosed a problem, I would hopefully have been able to have it fixed.