We found this great deal on HotUKDeals.

By using the following code you can get a 10% discount as well as the discount already on the site (£90 at time of writing, with 10 hours left) :

Dell (Business) Voucher: 10% off 479.00 – $8MSZDL6VTKBDS

Remember to reduce the warranty to minimum where applicable and take all Dell deals right through to checkout for final pricing.

Specifications:

305-D074203 Small Business site – Best price £464.72 Delivered.
Dell Vostro 420 (D074203)

Vostro 420 Standard Base Mini Tower Chassis
Intel Core 2 Quad Q9400 Processor (2.66GHz, 1333MHz, 6MB cache)
Genuine Windows Vista® Business with Service Pack 1, 32-bit – English
4096MB 800MHz Dual Channel DDR2 SDRAM [2×2048]
320GB (7200rpm) Serial ATA Hard Drive with 16MB DataBurst cache
512MB NVIDIA GeForce 9800 GT
Integrated 5.1 Channel Audio HD
Dell Entry Quietkey USB Keyboard – UK/Irish (QWERTY)
Dell 2 Button USB Optical Mouse
Norton Internet Security 2009 – 15 Month Protection – English
1Yr CAR Warranty – No Upgrade Selected
16x DVD +/- RW Drive

This is a great deal, especially as it’s also just dropped in price from £660.