I'm a fan of Lenovo laptops - have one myself - and there's a few in the £350-£400 range that are well specified and are even still obtainable with Windows 7 rather than 8.
I especially like the models with a proper numeric keypad, which is particularly useful doing spreadsheets.
For example:
20B2000KUK | Lenovo ThinkPad Edge E545 Quad Core 4GB 500GB Windows 7 Pro / Windows 8 Pro Laptop - Laptops Direct
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