Dell are having a 3 day special with extra memory, hard drive space and money off as well as some larger TFT monitors being offered.
Here is my pick of the Dimension offers, a nice quiet desktop unit that has a 19" TFT with it.
any-D07515 - £499 delivered
Intel® Pentium® D Processor 820 with DualCore Technology (2.80GHz,800MHz fsb,2x1MB cache) you could upgrade this to a D930 3Ghz dual core with 2x2meg cache for £35 extra
Genuine Windows® XP Home Edition, SP2
1024MB Dual Channel DDR2 533MHz (2x512) Memory
250GB (7200rpm) Serial ATA Hard Drive with 8MB DataBurst cache
16x max. DVD+/-RW Drive
McAfee® Security Centre 15-month Protection
128MB ATI Radeon® X300 SE HyperMemory graphics card. You could upgrade to 256meg x600 for £23 extra.
Dell E196FP 19" Midnight Grey (TCO99) Flat Panel Monitor
Integrated Audio with Dolby Digital 7.1 capability
Dont forget to reduce the warranty to 1yr and buy via Quidco for cashback savings.