From your post, it seems as though you are planning to build the system yourself. A shame about your budget. Although it is huge, its slightly short of a few hundred pounds to get the absolute enthusiast items.
From Ebuyer
CPU: Intel Core I7 2600k 3.4GHz Socket 1155 8MB Cache Retail Box Processor
Mobo: MSI P67A-GD65 P67 Socket 1155 GB LAN 8 Channel Audio ATX Motherboard
GPU: PALIT GTX 580 1536MB GDDR5 Dual DVI Mini HDMI Out PCI-E Graphics Card
RAM: Corsair Vengeance 8GB (2x4GB) DDR3 1600Mhz CL9 1.5V Non-ECC Unbuffered
PSU: Corsair Professional Series AX850 850W Modular PSU - 80plus Gold Certified
Case: Fractal Design Define XL Black
SSD: OCZ 60GB Vertex 2E SSD 2.5" SATA-II Read = 285MB/s, Write = 275MB/s 50,000 IOPS
HDD: Samsung HD103SJ Spinpoint F3 1TB Hard Drive SATAII 7200rpm 32MB Cache
DVD: Samsung SH-S223L 22x DVD±RW DL & RAM with LightScribe SATA Optical Drive - OEM Black
OS: Microsoft Windows 7 Ultimate - Complete package (Full Retail) - 1 PC - DVD - 32/64-bit
Total cost and including delivery is £1504.43
The MSI mobo for this week is currently offering 20% VAT cashback. Now Ebuyer is the only retailer not stating this on their website, so check with them since it looks like a manufacturer deal, rather than a retail one. This mobo supports multi GPUs and has a nice one button OC feature.
The system build includes an OS, which is a huge chunk of your budget, so instead of an after market heatsink and fan, the build sticks with the very decent stock cooler and should withstand the auto overclock, should you wish to use the MSI "OC Genie II" feature on your mobo.
The Fractal Case is huge, perhaps too big for your needs. But out of all the high end cases, its one of the most affordable.
Also check Aria, OverclockersUK and Scan to compare prices.
Aria have an excellent prebuilt machine, with the following components
CPU: Intel® 2nd Generation Core™ i7-2600K Overclocked @ 4.80GHz - Eight Thread CPU
Ram: 4GB Mushkin Ridgeback 2000MHz 7-10-8-27
Mobo: Gigabyte GA-P67A-UD4 Intel P67 (Socket LGA1155) DDR3 PCI-Express Motherboard - SLI Certified
GPU: NVIDIA® GeForce® GTX 580 1536MB Graphics Card
CPU Cooler(air): Corsair Cooling Air Series A70 CPU Cooler - 2x 120mm in push/pull
Case: BitFenix Colossus Venom Edition Full Tower PC Chassis
PSU XFX Pro Series 850W Single Rail PSU - GeForce® GTX 580 SLI Certified
SSD 40GB Mushkin Callisto deluxe 2.5" SATA-II Solid State Hard Drive (Boot drive)
HDD 1TB Samsung Spinpoint F3 HDD (Storage drive)
Blue Ray/DVD: Samsung Blu-Ray SH-B123L/RSBP 12x BD-ROM / 16x DVD Writer Drive.
The price is £1399.99 before any delivery costs.
The downside is that the PSU is not as highly regarded as the above, its SSD storage is smaller and it comes with less RAM(but very credible and excellent RAM). It also appears that no OS has been installed, but check to see if its possible to have an OEM installed for an additional cost. However the case itself is an eye opener and is excellently built, the Mobo is as good/similar to the MSI/Asus Pro mobos out there in terms of features and multi GPU support, the CPU comes pre-overclocked with an aftermarket Heatsink and Fan and it comes with a Blue-Ray Drive.
They also disclaim
Please note that adding in additional memory to the spare slots will require new BIOS settings and the maximum clock speed attainable may be significantly reduced. Updating the BIOS will disable and remove the Overclock.