I do not like your behavior but here is the build You wanna go for:
http://uk.pcpartpicker.com/list/rk9cf8
GTX 1070 is utterly overpriced GC due to lack of competition from the AMD side. Not to mention Nvidia sux under DX12 that is made by Microsoft and AMD.
The headphones You chose are actually not bad as reviewed by LinusTechTips tho a high quality 5.1 system or something will definitely make your PC experience better.
For mouse and keyboard mmm ... depends on what games you play and if you are hardcore or casual player. I am hardcore WoW player so for me Logitech G600 is a must MMO mouse. Also I feel comfortable with chiclet keyboard only so I'd go for Razor Deathstalker.
But as your budget is "only" 900 pounds I'd get the computer together with the headphones and used some old mouse and keyboard till I can afford something better. Or you can sacrifice additional LED fans as they are not needed that badly. You can always buy them later and save 40 pounds now.
The PC I built has high OC potentional, great "cooperation" between parts, super stylish look (for me this is important too), fits your budget and together with RX 480 and preferably 144Hz 1080p FreeSync monitor this is THE BEAST.