These are the Dell laptops I could come up with that are likely to be suitable, but exceed your budget (except the 1st perhaps if you're able to get the discount). The main reason for choosing them is that they have reasonably good graphics with a HD 550v or GT 420M.
£529 Inspiron 15R (Inspiron N5010 BTS) click here: i3-370M / 4Gb / 500Gb / HD 550v
It's £499 if this money-off voucher is still valid when you place your order: NPV61RB0F4$437 (1st 500 units & expires TODAY 5/12. It did for me at the time of posting this - a screenshot: click here
£529 XPS 15 click here: i3-370M / 2Gb / 250Gb / GT 420M
£549 XPS 15 click here: i3-370M / 3Gb / 320Gb / GT 420M
Here's a laptop graphics (GPU) benchmarks list with respect to games click here. WoW is 4th from extreme left - FM11 is not mentioned, but thankfully it doesn't need a monster spec. Anything up to & above the 'NVIDIA GeForce 8600M GT' should be good enough for the games you intend playing - so there's a vast choice of laptops (non-Dells) out there to choose from. The rest of the spec in terms of the CPU should be good enough too, so you'll need to check if the RAM & hard drive meet your desired spec. G