Build advice Gaming PC advice

Hi guys a friend of mine asked me if I know of any good Gaming PC`s out there for his son
I don`t have a clue about them so this is why am asking here
He wants to spend around £350
from anywhere really online or local shops IE Amazon/PCworld/Ebay etc
Just wants it all in one not to build himself.
Any links or advice would be great
Thank You.

Something like this will play most games at medium to high settings: ULTRA FAST QUADCORE AMD 4.3GHz GTX 750 Ti 2GB Graphics 8GB 1TB Gaming PC 195017 | eBay