I'd be surprised if you need to spend 400 quid for a suitable laptop. Your requirements are pretty much word for word the same as mine and my 2 1/2 year old laptop has performed flawlessly, never had an issue of any kind. By todays standard the specs would appear a bit ordinary (it was a baseline model at the time) i.e. 40 G hard drive, 1 G Ram and 'only' 1.4 G processor, but it does the job. I've never considered it to be slow or not up to it, probably because like you I don't have any serious demands of it..
My machine is a Toshiba Satellite L10, and contrary to other's opinions, I would not hesitate to buy another Toshiba if I needed a new machine. For example today I got some junkmail offering a Toshiba Satellite Pro A200 with 1.6G processor, 1G ram and 80G HD for A$700 or about 300 quid. Probably all you need?
Cheers
Octane