Computer for WoW

Hi,
My PC just broke and ive been looking for a new computer since on my old computer i played wow on low settings reaching 15 fps max and now im hoping to find a computer what plays 30 fps+ i usuallly raid a fair bit and spend time in dalaran.
I live in the uk and have a budget of 300-400 pounds, i dont really want to custom build it since i am not great with computers but i guess im up for a try if you could help me  


P.S speak with less computer talk thx