I am not overly impressed with PC World at all. Expensive, poorly trained staff (some good, most not).
I had to argue (who, me?) over statutory rights, when my laptop failed after a couple of weeks "...not fit for purpose...", "...not interested what your policy is... statutory laws take precedence..."
I have asked to speak to the 'store expert' as advertised... only to be told "you are talking to him"... Sorry. Off high horse now.
I can recommend Currys; their range is smaller than before, but their prices are really good (and you CAN haggle!!!). Also, Staples who also have good, knowledgeable people and are very good at honouring warranty claims.
Personally, I'd also only buy a recognised main make, not one that I hadn't heard of before.