Just a couple of things to bear in mind....
1. you sound like a non PC person - therefore you won't be wanting to/know how to fix the software problems that will inevitably go wrong with it at some stage (be it a virus, user error or whatever). Buy new, so it has a clean install that you can always revert to when the wheel comes off. You'll also have a 12month minimum warranty if hardware breaks; (which is more likely in the first 12 months).
2. You've already set your budget. Stick to it. Everyone will be able to suggest something slightly better "for an extra £20" and you can very quickly spend too much.
3. As a student, you're not likely to be in a position to be able to afford to throw £50+ odd at it to get it sorted in 3 months or more time if it goes wrong.
4. You know what you want it to do. ALL laptops/netbooks that are off the shelf (be it Tesco/Asda/PcWorld/ariapc.com etc) will do what you want it to do.
Taking all of the above into account; go into the shops, have a look and feel of the working examples on display and go for the one that you like the look of the screen quality and feel of the keyboard / size & weight etc.
Take note, of the EXACT model number and do a quick check online to see if you can save a couple of quid. if not.....Buy it
When it comes down to it, on your budget, it's down to what looks/feels good.
