UserSmart - You have exactly the same issue as me! Except I have no proof of purchase as it was paid for with cash and my GF has lost the receipt, only ourselves to blame for that error
Since you have proof of purchase, follow gwynevans' advice and bring up the sales of goods act with Waterstones. See my letter i quoted above...well it doesn't really apply to Sony, it applies to the retailer who are Waterstones. I'm very sorry this happened to you, but I'm relieved to hear my case isn't a one off!! Please keep us informed, I'd really like to know how you get on.
Mark