Ok -UPDATE - I took it back to overclockers who had it for just under a week, They said the overclock wasn't set up correctly, they ran a 3d mark in store and my set up now achieves a score of approx 17.5k, which sounds about right from what you guys said.
HOWEVER, i turned on WoW when I got home, upped all the graphics settings to full. BAM crash!
Its getting beyond a joke now, they said they run all sorts of test while they had it with no crashes, they even played grid on it in store and it didnt crash (which they gave me free which I thought was generous)
I am in the process of re-installing WoW now, but reading the WoW forums it seems alot of people have this problem, I'm starting to think maybe its a game related problem ? I'm not really sure
Any1 got any more ideas ?
/cry Rich