As usxhe said I would definatly go for a CULV laptop over an Atom powered one they just feel so much faster. Scan have a viewsonic viewbook 120 for £325 which is a 12" laptop and dual core celeron with windows 7. While its not the fastest thing out there it beats an atom hands down.
http://www.scan.co.uk/Products/121-V...Windows-7-Home
The website below, I found quite helpful for comparing laptops and searching for ones you might be interested in. Its has links to two reviews on the viewsonic.
http://www.notebookcheck.net/Viewson...0.25133.0.html