Thanks for the replies guys. I dont think il be going down the Grado route as i have read on a few sites that they produce a very narrow soundstage and are not good at all for positional audio.
I have narrowed my choice down to Sennheiser HD555, HD595, PC350 or the HD380's also i dont mind sound leakage at all to be honest. Aslong as the sound quality is good, soundstage is good and positional audio is good i dont mind spending about £100 or even abit more.
The only thing with the game dedicated PC350s is that iv read they dont produce much bass unless you open them up and do a little mod which i dont mind doing but if some headphones already sound better then i could just avoid the hassle.