I'm going to book it into my local garage to pressure test the cylinder head and see if that's what's causing the problem.

That's for your advice and links. I'm working my way through those, although a lot of the info is stretching my ability the understand!

Thanks for the reply Geoff. Yes it's a diesel. It got very hot when it failed, but I think I was able to pull over soon enough that it wasn't running overheated for very long after the coolant all dropped out.

There's no smoke blowing out the back and the oil looks clean - are there other signs I ...

Hi, we've been at it 3 days on and off now, trying to bleed the coolant after changing out the pipes (one split under the passenger seat so we had to be towed home - thought it best to replace the lot while we're there, given that I seem to have managed to avoid blowing the head gasket :shock ...