PCPartPicker part list:
http://uk.pcpartpicker.com/p/3KyKz
Price breakdown by merchant: http://uk.pcpartpicker.com/p/3KyKz/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/3KyKz/benchmarks/
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor (£160.79 @ Aria PC)
Motherboard: Gigabyte GA-Z87-HD3 ATX LGA1150 Motherboard (£75.79 @ Amazon UK)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory (£49.98 @ CCL Computers)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£36.79 @ Amazon UK)
Video Card: PowerColor Radeon R9 290 4GB PCS+ Video Card (£295.19 @ Aria PC)
Case: Corsair 200R ATX Mid Tower Case (£39.95 @ Amazon UK)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply (£45.26 @ Amazon UK)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) (£69.95 @ CCL Computers)
Wireless Network Adapter: TP-Link TL-WN881ND 802.11b/g/n PCI-Express x1 Wi-Fi Adapter (£12.00 @ Amazon UK)
Total: £785.70
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-15 18:38 BST+0100)
I added an OS and a WiFi card. To compensate for costs, I had to downgrade the PSU (It'll still run your computer well. It has 46A on the 12V rail, which is 554 watts for your components). I also had to downgrade from the R9 290X to the R9 290, which is practically negligible, the 290X is just the 290 overclocked.