These seem like an excellent deal. Yes they are refurb, but they include a 12 month warranty with Dell, and all Dell refurbs I have had in the past have been excellent (maybe a couple of slight marks). If you receive it and aren't happy, you can always return it to your local Currys store or arrange collection. Use the attached 5% voucher to get it down from £399.97 to £379.97 and delivery is free. Quidco also available at 3% (roughly £11.39 making this £368.58 if it pays out).
Product code: 758254
Intel Core 2 Duo Processor T5750 (2.0 GHz, 667 MHz FSB, 2 MB Cache)
Genuine Windows Vista (R) Home Premium
4 GB Memory
320 GB Hard Drive
Blu-Ray Combo DVD drive
15.4" TrueLife Widescreen
256MB ATI Radeon 3450 Graphics
Colour - Blue
I bought one of these back in September for £430 IIRC, so at £50 less it is a steal. They also have a red one, but that is £30 more (£429.99 - product code: 684755). Stock is usually very limited on th refurbs, so get one ASAP if you're after one.
They have some other refurbs in, but as far as value for money goes, the Studio 15 is a robust machine and this spec is excellent.