This would be better:
MO-001-DE Dell Ultrasharp 2405FPW 24" Widescreen LCD Monitor - Midnight Grey (30906) (MO-001-DE)
£559.95 £559.95
KB-015-RA Razer Copperhead Tempest Blue 2000dpi High Precision Gaming Mouse - Retail (KB-015-RA)
£39.95 £39.95
KB-015-SK Saitek PZ30AU Eclipse Illuminated Keyboard (KB-015-SK)
£24.95 £24.95
CP-151-AM AMD Opteron UP 165 Dual Core San Diego 1.8GHz 2MB Cache (Socket 939) - Retail (CP-151-AM)
£204.95 £204.95
HS-003-SY Scythe Ninja Plus Heatpipe CPU Cooler (Socket 478, 754, 939, 940, LGA755) (HS-003-SY)
£26.95 £26.95
MB-014-DF DFI LanParty UT NF4 Ultra-D (Socket 939) PCI-Express Motherboard (MB-014-DF)
£79.95 £79.95
MY-057-OC OCZ 2GB (2 x 1GB) PC3200 Dual Channel Platinum Series EL-DDR CAS2 (OCZ4002048ELDCPE-K) (MY-057-OC)
£139.95 £139.95
GX-060-PC PowerColor ATI Radeon X1900 XT 512MB GDDR3 AVIVO TV-Out/Dual DVI (PCI-Express) - Retail (GX-060-PC)
£249.95 £249.95
HD-070-WD Western Digital Caviar SE16 320GB 3200KS SATA-II 16MB Cache - OEM (HD-070-WD)
£69.95 £69.95
CD-033-NE NEC ND4571 16x16 DVD±RW Dual Layer LabelFlash ReWriter (Black) - OEM (CD-033-NE)
£24.95 £24.95
CA-096-CM CoolerMaster Stacker RC-810 - Silver Trim (No PSU) (CA-096-CM)
£89.95 £89.95
CA-024-EN Enermax Liberty 620W ELT620AWT ATX2.2 Modular SLI Compliant PSU (CA-024-EN)
£84.95 £84.95
Subtotal £1,596.40
Shipping (City Link Parcel Next Day (Delivered Mon-Fri)) £24.95
VAT £283.74
Total £1,905.09
A single x1900xt 512mb is faster and better than 2 7900gt's 256mb sli'd! + you'll need 512mb memory if you're running that screen!
You forgot a CPU cooler, you'll need a good one with an Opty.
The PC3200 ram I spec'd is just as good as the PC4000 and some would argue better because of the tighter timings.