Ok heres what i have so far, all the parts you've listed.
CPU - Intel Core 2 DUO E6400 £149.21 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=CP-127-IN
CPU Cooler + Heatsink - Arctic Cooling Freezer 7 Pro £16.44 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=HS-017-AR
Motherboard - Asus P5B Deluxe £123.36 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=MB-150-AS
Memory - Corsair 2GB DDR2 XMS2 Dominator £205.61 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=MY-124-CS
Graphics Card - BFG GeForce 8800 GTX 768MB £399.49 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=GX-035-BG
Power Supply - Corsair HX 520W ATX2.2 Modular £70.49 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=CA-005-CS
The E6400 will overclock above the E6600 speeds quite easyily so no need to get the E6600.
If your looking to overclock you will need another CPU Cooler and Heatsink the one that comes with the Processor just wont cut it.
Total : £976.30