£500 Budget tops

Hello,
1_My budget is £500 tops

2_I'd really like at least a 15.6

3_I game so a reasonable picture is a must have 1024x768 as a bare minimum better would be good

4_I don't understand which I need a portable or desktop replacement laptop?

5_Some of the gaming I do is long sessions so at least 2 preferably 4 or 6 hours would be good

6_I play a number of different games o f many different genres from Evony through WOW to Total War

7_Other tasks are writing in Word and pdf form running spreadsheets etc...

8_Storage wise I'd like 500GB

9_www.aria.co.uk/www.ebuyer.co.uk/pcworld as a last resort

10_Its going to have to last 3 years and I know thats quite long

11_4GB would be a good memory option with a dedicated low end graphics running at least 500mb onbrd

12_This will be my 1st laptop so I don't know which manufacturers are best but I saw what I thought was a brill deal on aria /MSI CX620 buts now out of stock

13_I'm in the UK


14_I'd just like your best answer and I know it'll be a compromise