Originally Posted by BigDog
suppose i could change it to an i7, what else would need to be changed if i did so?
Assuming the processor is the same socket type (LGA1151 in this case), nothing else will need to be changed.
Adding on to my previous post, at your budget you simply won't be able to get the best of everything. From both a future pricing standpoint and for ease of replacing components, it's a better investment to shell out the extra cash for the CPU. You won't need to change that for at least five years, assuming the research speed in that area stays as slow as it's been recently. Your graphics card will need to be upgraded a little more frequently, but due to the competitive market in that area, better components will be available at lower prices, and it is much less of a headache to switch out than a processor.
EDIT: Also what Smaguris said. I can run Fallout 4 on almost max settings (with lots of mods) with an average fps of 50 with a GTX 1060. If you absolutely must have a high end card, at least compromise and get a 1070. Almost as good as a 1080 in performance and £150-£200 cheaper.