I don't think you are going to get a "gaming laptop", for that low. At least not a laptop good enough to call a gaming laptop - others may disagree. My personal opinion is that you can/will get a lot more for your money (spec.wise) with a desktop than a laptop.
I will continue to look around for you but in the meantime maybe someone else may be able to offer further advice.
I often use the PCA reviews to guide me with purchases. The latest September issue praises the Medion Erazer X6811. I quote "The nVidia GeForce GTX 460M is a meaty graphics processor........it takes gaming at healthy resolutions in its stride."
I speak from no personal experience and the price tag, about £800, is at your top end price, but it is worth a look.