The bit thats worrying me is the fact that they did 3 sniff tests and 3 compression tests that came up clear. They rekoned the headgasket was ok.
It was only the fact that I got fed up and told em to strip the engine cos I was fed up with the overpressurising. When they stripped the engine it was found that the head had been shifting on the nylon dowels and that the HG WAS gone. They then skimmed and pressure tested the head and re-fitted it.
Now suddenly the head is cracked TWICE and they missed both of em. I'm starting to wonder just how much knowledge engineering companies have.