Help and advice wanted.

So grizz has decided to upgrade the old wreck, but Grizz is on the move a lot these days, the chunky desktop computer for the moment will not do!

Anyway I am looking at getting a laptop, the main thing I will be using it for is gaming, yes I know desktops are better for gaming but I am not expecting to play the absolute latest games on highest graphics, aside from the odd Fifa and Total war a lot of games I play are a good few years old...

I want to play Dues Ex Human revolution on my new computer, because it doesn't work on the current one.

So I have a budget up to around maybe 600 (700 at a real stretch) I live in the UK, so shipping costs to be taken into account.

I would rather not use something that isn't too widely used online, never actually shopped online so I would like to make my first purchase on there fairly reliable. Also I am a student so not sure if that may help me get a discount in some places...

Wasn't sure whether to put this into the tech section, although it isn't really all that tech heavy and is more like purchasing advice, so feel free to move it if it is in the wrong place.

Ohh and ideally I would like at least a 15" screen, 17" would be great but seems an unrealistic aim... just trying to get the most powerful I can for the least money really.