Back to Mr VonSwirl's problem,

Does your stud look a bit like this, but stuck in the head.



I used a cold chisel on the edge of the base 'flange' to unwind the broken stud.

It helped that I had previously cleaned the thread (stud and hole) and had applied anti seize before screwing it in.

As the NEW studs also stretched (and 1 broke) before reaching their stated torque, next time (if there is one) I'll just use normal M8 studs and torque carefully.

Not impressed with this stud type.

Deano