I have put together a gaming rig in which is in and around your budget;
Case
COOLERMASTER HAF 922 MID TOWER GAMING CASE (£82) Processor (CPU)
Intel® Core™i7 Quad Core Processor i7-930 (2.80GHz) 4.8GTs/8MB Cache Motherboard
ASUS® P6X58D-E: DDR3, USB 3.0, SATA 6.0GB/s, 3-Way SLI Memory (RAM)
6GB KINGSTON HYPER-X TRI-DDR3 1600MHz, INTEL X.M.P (3 x 2GB KIT) Graphics Card
1536MB NVIDIA GEFORCE GTX480 GDDR5 PCI EXPRESS - DirectX® 11 Memory - 1st Hard Disk
1TB SERIAL ATA 3-Gb/s HARD DRIVE WITH 16MB CACHE (7,200rpm) 1st DVD/BLU-RAY Drive
24x DUAL LAYER DVD WRITER ±R/±RW/RAM Memory Card Reader
INTERNAL 52 IN 1 CARD READER (READS XD, MS, CF, SD, etc) Power Supply & Case Cooling
CORSAIR 850W PSU (TX850) 80+ ULTRA QUIET (£100) Processor Cooling
COOLIT ECO A.L.C (ADVANCED LIQUID COOLER) (£62) Sound Card
ONBOARD 8 CHANNEL (7.1) HIGH DEF AUDIO (AS STANDARD) Network Facilities
ONBOARD 10/100/1000 GIGABIT LAN PORT USB Options
6 x USB 2.0 PORTS @ BACK PANEL (MIN 2 FRONT PORTS) AS STANDARD Operating System
Genuine Windows 7 Home Premium 64 Bit - inc DVD & Licence (£79)
With this you get a great CPU, Liquid Cooling, 1TB HDD, nVidia GTX480, Corsair T850 PSU - what more could you want Let me know if you have any questions!
sounds really good, do i need to have usb 3.0 and for network facilities is it worth getting the wireless 802.11N for wireless internet capabilities, also what would be the best graphics card down from the GTX480, sorry about all the questions and thanks for the help