Well looks like my sons friend is now looking for a pre-built PC.. i understand why he though he wants a warranty and building your own is risky.
I'd like to thank everyone for there input so far, but as he now wants to have pre-built i have to start the search again.
He has a Budget of £700 for a pre-built (£100 more than before, but i know that building your own is normally much cheaper.. oh well)
So he does not need a keyboard-mouse or Monitor as he is re-using those parts, any suggestions would be welcome