I recommend a G3258 it's cheaper than 90 pounds and you can over clock it. A little more money can get you a non k i5 like the 4440 which is a Quad Core.
No worries, but I just don't see beating that game performance of a 7700k on £90. In the states, with the equivalent $140, you certainly could, but in the UK not so much.
The 7700k pulls 70fps in arkham origins, while the 730 averages 52.
http://www.eteknix.com/complete-amd-kaveri-review-a10-7850k-a10-7700k-a8-7600/11/ http://www.tipidpc.com/viewreview.php?id=1107