Choosing a laptop with a budget of £500 - £700.

Hi there folks I just wanted a bit of help choosing a good solid laptop that will last me for a few years because I will be starting University in Sept 2013. I've been looking at mostly i5 - i7 laptop or high end AMD APU Laptops.

My needs are simple, I want a laptop with a dedicated graphics chip that can or will play most games on medium to high (BF3 as a benchmark maybe?), a good solid Intel CPU i5 or i7? or high end quad core AMD CPU, 4GB+ RAM, 500GB HDD or 250GB SSD, looking preferably at a 15"+ screen (can be touchscreen) and preferably an ultra book or VERY Light laptop with Windows 8.

Any help is appreciated  

Thanks.