Just to clarify (please don't go any more explicit on the uses than you have to) and make it sound a little less dodgy, you want a basic file server/download box? In which case something like the below system ought to fit the bill, onboard graphics and all other necessary parts to build a basic PC, if you can find an extra £10 or so it might be worth going for 2gb Ram.
Hitachi Deskstar T7K500 320GB SATA-II 16MB Cache - OEM (0A33435) £43.99
(£51.69) £43.99
(£51.69)
AMD Athlon 64 X2 Dual Core 4000+ 2.10GHz (Socket AM2) - Retail £34.99
(£41.11) £34.99
(£41.11)
Corsair 1GB DDR2 Value Select PC2-5300C5 Dual Channel Kit (2x512MB) (VS1GBKIT667D2) £13.99
(£16.44) £13.99
(£16.44)
Asus Vintage V3-M2V890 Barebones System - AMD64 (Socket AM2) £51.99
(£61.09) £51.99
(£61.09)
LiteON DH-20A4P-21C 20x DVD±RW IDE Dual Layer ReWriter (Black) - OEM £13.99
(£16.44) £13.99
(£16.44)
Sub Total : £158.95
Shipping cost assumes delivery to UK Mainland with:
City Link Parcel Next Day (Delivered Mon-Fri)
(This can be changed during checkout) Shipping : £9.95
VAT is being charged at 17.5% VAT : £29.56
Total : £198.46