YAHOO! I GOT IT OUT! and I didn't even sacrifice a virgin ( not easy to find here in Essex anyway )
I think I was lucky but it was in there very tight. heres how it went just in case it helps someone else. I soaked overnight in penetrating fluid, a quick tentative feel with mole grips showed it to still be 'somewhat stuck' I purchased a 'Professional stud extractor set' ( their words not mine ) from Halfords, Machine Mart do the same thing. These are devices that look like large spark plug sockets which have 3 eccentric doobreys ( sorry to use a technical term ) inside which grip the stud, the more pressure you put on the tighter the stud is gripped. The 8mm one can just be fitted over the stud in question, it is a VERY tight squeeze and I had to tap it on just slightly bruising the the fin below but nothing to worry about as it won't be seen. I applied heat with a blow torch attempting as far as possible to heat the alloy rather than the stud applied a little candle wax then on with the extractor and with a bit of fiddling out it came, I couldn't believe it.
Not sure the wax made any difference but I had seen it used in a u toob vid so I figured it couldn't hurt. I found the head fin below the stud tended to push the extractor slightly off line so at first it didn't want to grip but with a bit of fiddling and pushing it against the fin eventually it did.
Anyway I am off to the pub to celebrate