Thanks to all for the advice.
I decided to put the new head gasket on it and see what happens.
So, last night I was back under her, sump back on, then after cleaning the head up as best i could a put it back on.
TENSIONED DOWN CORRECTLY and so far the only thing in the sump is oil. Radiator is full. So thats a good sign.
I rechecked it all this morning and apart from a couple of oil drips where I pulled the tappet cover back off last night things were still looking ok.
I guess the real test will be when i try and put a fire in her belly.
If I have the same problem then out she'll come and get the full rebuild I was really hoping to put off until after Xmas this year.
you blokes really are a true wealth of information. Even when the old girls on the road I think I'll hang around here.

Not all chemicals are bad. Without chemicals such as hydrogen and
oxygen, for example, there would be no way to make water, a vital
ingredient in beer