Right, I've got a bit more money than I thought I would have, so I've doubled the budget to £1000. f I can get lower, then good.
The 2 models I've been looking at are the Asus N55, which seems to come with i7, 1600x900 screen and blue ray, for £750, but there's not many around. PC world have them on their site but not available for delivery and seemingly not available for pickup no matter what postcode you put in. There is an i5 version for £699, but you may as well pay £50 extra for the i7... The other option is the Samsung Chronos, which I think is beautiful, but expensive. £799 gets you the base i5 version, with only Intel graphics, £899 from JL gets you the same but with ATI graphics, and £999 from JL again gets you the i7 version.
Anyone got either of these machines/know anything about them. There are a few Chronos reviews out there and they're mainly positive, but I haven't seen any for the N55 yet.
Edit: For anyone mentioning alternatives (which I welcome) screen resolution must be at least 1600x900...