I would get a Lenovo X220.
I already have one, it's the best freaking laptop I've ever owned.
On eBay you could pick one up, roughly your spec (smaller hard drive) with money to spare that could pay for a SSD to make it really fly: http://www.ebay.co.uk/itm/Lenovo-ThinkPad-X220-12-5-320-GB-Intel-Core-i5-2-5-GHz-4-GB-Laptop-/130772072383?pt=UK_Computing_Laptops_EH&hash=item1e729f77bf#ht_526wt_1141
@Velocio started
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I would get a Lenovo X220.
I already have one, it's the best freaking laptop I've ever owned.
On eBay you could pick one up, roughly your spec (smaller hard drive) with money to spare that could pay for a SSD to make it really fly:
http://www.ebay.co.uk/itm/Lenovo-ThinkPad-X220-12-5-320-GB-Intel-Core-i5-2-5-GHz-4-GB-Laptop-/130772072383?pt=UK_Computing_Laptops_EH&hash=item1e729f77bf#ht_526wt_1141