PCPartPicker part list:
http://uk.pcpartpicker.com/list/YzQ7hq
Price breakdown by merchant: http://uk.pcpartpicker.com/list/YzQ7hq/by_merchant/
CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor (£212.33 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£29.99 @ Amazon UK)
Motherboard: Asus Z170-A ATX LGA1151 Motherboard (£127.99 @ Overclockers.co.uk)
Memory: Kingston HyperX Fury Black 16GB (2 x 8GB) DDR4-2133 Memory (£59.99 @ Amazon UK)
Video Card: MSI GeForce GTX 1070 8GB Video Card (£398.29 @ CCL Computers)
Total: £828.59
You could get the 6700K if u wanted but the i5 is enough for gaming purposes