Tony, (and Dan)
I would questions the head gaskets to be honest 1st , I have never liked Cometic gaskets, when you strip a motor fitted with a Cometic gaskets they are never stuck to either the head gasket/block not like HKS or oter makes of Metal gaskets.
But the problem you have just had are a real head ache to sort out , people think just bolt the cylinder head on tighter that will sort the problem but it doesnt work like that I am afraid.
good luck any questions ask away.
Mark