no idea about price in england, the price in the USA is supposed to be at $379 or $50 more then the 970 released at. The 1070 is rumored to perform at around the GTX 980
I would hang on a few weeks after the nvidia launch. AMD's launch is supposed to be within weeks of the Nvidia launch and it promises to be cheaper for the "similar" cards and potentially (if benches/rumors are to be believed) even faster then pascal, with the r9-470 matching or performing close to the 980ti (if rumors are to be believed)