I have decided to try and help out any of us brits who are in need of a high-end gaming PC for between £850 and £900.
Please feel free to improve/substitute any parts
CPU: Intel i5 2500k
http://www.ebuyer.com/product/251596
RAM: Crucial 8GB cl8 1600Mhz 1.5v (x2=16GB)
http://www.ebuyer.com/311813-crucial-8gb-ddr3-1600mhz-ballistix-tactical-memory-blt2cp4g3d1608dt1tx0ceu
CPU Cooler: Corsair H60
http://www.ebuyer.com/264011-corsair-hydro-series-h60-high-performance-liquid-cpu-cooler-cwch60
SSD: Samsung 830 128GB
http://www.ebuyer.com/318421-samsung-128gb-830-series-ssd-kit-mz-7pc128d-eu
Motherboard: Asus P8Z68-V/GEN3
http://www.ebuyer.com/291652-asus-p8z68-v-gen3-socket-1155-dvi-vga-hdmi-8-channel-audio-atx-motherboard-p8z68-v-gen3
PSU: Corsair TX650 V2
http://www.ebuyer.com/257232-corsair-tx-650w-v2-psu-80plus-bronze-certified-cp-9020038-uk
Case: Coolermaster HAF 912 Plus
http://www.ebuyer.com/239757-coolermaster-haf-912-plus-case-rc-912p-kkn1
Wireless Card: Cheapest PCI card :P
http://www.ebuyer.com/276538-tenda-w311p-wireless-n150-pci-adapter-w311p
Optical Drive: Cheapest 24x RW
http://www.ebuyer.com/410560-liteon-ihas124-24x-dvd-rw-dual-r-ram-sata-drive-internal-black-ihas124-19cu
HDD: Western Digital 500GB Caviar Blue 7200rpm 16mb cache
http://www.ebuyer.com/241715-wd-500gb-blue-desktop-drive-wd5000aakx
GPU: XFX Radeon 7950 Dual fan (free games "AMD never settle" deal)
http://www.scan.co.uk/products/3gb-xfx-radeon-hd-7950-double-d-5000mhz-gddr5-gpu-800mhz-dvi-dvi-hdmi-mdp
TOTAL: £885.58
All parts from reliable merchants with great customer service and delivery times.