** £199.99, but £159.99 15th June only using code CTWENTY when you pay using Paypal (one per Paypal account apparently). **
There are lots of 4GB laptop deals on this site, but this one has 6GB so may run a bit more smoothly if you have several programs running. The AMD A6-6310 quad core processor is no slouch, scoring 2348 points on http://www.cpubenchmark.net.
I believe it runs efficiently and the listing states "up to 7 hours of battery life".
The laptop has a 1TB hard drive and DVD rewriter, stereo sound, and comes with Windows 8.1 so an all round good package for under £200.