im sure it's not just an £800 machine. It will have customisation a that make it range in price.
To get the best it offers you would be looking closer to £1500. The gtx980 is £500 on its own.
EDIT - posted before I read the thread.
A gtx750 isn't going to get good settings in wow and I think never winter is more demanding.
You can get a lot better than that at OCUK. I actually have better in my basket in OCUK for £850 ATM. Better CPU GPU case and ram. CPU cooler and an SSD.