PhaTTy, are you n/a or turbo? (just was wondering due to the P90 reference)
When the gasket has let go, what were you doing? Were you driving it hard, or were these easy break in miles? What torque did you use on the headbolts?
I too tend to believe that you may have an issue w/ the block surface after going through 2 different heads.
BTW, if this is a turbo car, then you may be going the wrong way with your compression ( N47 and 1mm gasket ), depending on the boost pressure you are trying to run...
Regards,
mike