Re: Decent GPU circa £50-65
A little more than you're looking at, but R7 260x 2GB for £78 at CCL seems a pretty good deal - http://www.cclonline.com/product/135...yPort/VGA2238/
WoW can also be fairly CPU hungry and it favours Intel over AMD CPUs quite heavily. If you find the GPU upgrade doesn't improve things enough then it may be worth looking at an i3, or even the Pentium Anniversary edition. Normally I'd say go for an AMD cpu if you're on a budget, but not for WoW (or Diablo 3 and possibly SC2).
Re: Decent GPU circa £50-65
Quad core C2D CPUs come at reduced price on eBay if your MB supports it.
But can only second the R7 260X. An rather excellent card value wise.