When I bought my MP3 player from them (a fair while ago, now) I ordered a 40Gb one... They sent a 20Gb... Rang them up, said "er.." nice bloke immediately arranged an exchange, Parcelforce picked up the 20 and swapped it for the 40 right there and then on my doorstep (nice!) and then a little while later... They refunded me the entire amount!
I emailed back a month or so later to ask whether they realised they'd actually exchanged, not refunded, because if they realise they made a mistake they're fully within their rights as a company to take the money out of my account, but I never got a response... So, free MP3 player.