You're looking to purchase in the most competitive segment of the graphics card market, so be prepared for plenty of options!
And the need to find some Asprin fairly soon.
I'd stay away from the R9 280X, too much extra cash for the fairly small performance improvement over the R9 285 or R9 280.
I'd consider the R9 280/285 or Nvidia GTX960:
Much as it pains me as a die hard AMD fanboi to say so but the top dog in this price segment really has to be the GTX960, it's around the same performance of the R9 280/285 and can even nip the heels of the R9 280X in some games, runs cooler and draws a lot less power, the custom cooled cards are reported as being virtually silent. It's biggest drawback is the higher cost...But it is within your £180 limit.
The R9 285 is a bit slower and burns more juice but is significantly cheaper than the GTX960, it is also Freesync compatible and the True Audio is handy if you hook up to a monitor or TV through HDMI.
The old man of this little group is the R9 280, a card whose roots reach back to the over 3 year old HD7950, still, it's DX12 compatible and has 3Gb of memory, not 2Gb as the other cards have, the extra 1Gb helps to smooth things out because the cards with less memory tend to need to load data more often, which does cause glitches.