So I log out earlier as my game is hanging, stuttering and generally glitching to hell (nothing else going on on my system so had to be a problem with WoW).
Restart PC. Log back in and its even happening on login - taking ages to load, stuttering on char selection etc.
So use repair tool and it basically does fuck all. So now Im redownloading the game (moved all my addons out of the way so i dont go thru that nonsense again) and reinstalling.