[Monitor] 22" Neovo H-W22 V2 Widescreen LCD, 1680x1050, DVI, 2000:1 DCR, 300 cd/m2, 3 ms, Speakers, VESA £152.15
I picked up a 19" widescreen from scan for £111, do you need the extra 3"?
[Keyboard] Saitek PK 02AV Eclipse II Wired Keyboard, BackLit Purple, Red + Blue Keys, USB 1.1/2.0, Black £23.37
Typing on one now
[Mouse] Logitech G5 Laser Mouse, 2000dpi, USB 1.1/2.0, 4 Buttons, Silver/Black Retail £31.60
[PSU] 520W Corsair HX Series Modular PSU, ATX, EPS12V, whisper quiet, 5 year warranty £60.97
[Case] Akasa Eclipse-62 Midi Tower Case - Hi-End w/o PSU - Best Seller £87.88
You can get a good case for a lot less than this. I'm using an Antec 900 £70
[Mobo] Abit IP-35 Pro, iP35 Express, S 775, PCI-E (x16), DDR2 667/800, SATA II, SATA RAID, ATX £108.68
the PRO has very little advantage over the standard IP-35.
[CPU] Intel Core 2 Quad-Core Q6600 G0 SLACR, 95W, S775, 2.40 GHz, 1066MHz FSB, 8MB Cache, Retail £152.62
Unless you're planning on doing multiple CPU intensive tasks at once, try a C2D. You'll get one with as much power per core for maybe £100. Quad offers no advantage for gaming, yet. And when it does, the Q6600 will be at the bottom of the list.
[GFX] 512MB MSI 8800GT OC, PCI-E 2.0 (x16), 1900 MHz, GDDR3, GPU 660 MHz, 2 x Dual Link DVI-I, HDTV £169.16
[RAM] 4GB (2x2GB) Corsair TwinX XMS2, DDR2 PC2-6400 (800), 240 Pins, Non-ECC Unbuffered, CAS 5-5-5-18 £86.53
4Gb (1Gb) would also work. I'm using geil, no problems yet, and cheaper than the Corsair.
[HD] 400 GB Samsung HD403LJ Spinpoint T166, SATA II, 7200 rpm, 16MB Cache, 8.9 ms £54.27
[DVD Burner] Samsung SH-S203D/BEBN 20x DVD±R, 12x DVD±DL, DVD +RW x8/-RW x6, SATA, Black, OEM £18.20
[OS] Microsoft Windows Vista Home Premium 64Bit 1Pk OEM (DVD) £63.91