christmas gifts argos

Is it true that you do not need a receipt to return unwanted Christmas presents?
Hi – Is it true that you do not need a receipt for gifts. My grandparents are going to buy me a 360, but I already have one. so they want to maintain their one (because it is more likely to be a newer model) but my other 360 I can take a 06 model to places like game or Game Station Argos, Tescos etc without a receipt. I do not want to sell on eBay and I care if their vouchers. I have also heard on GMTV in the morning, a man anbout talking about everything – the returns policy, trade and so any links or experience or expertise is greatly appreciated, thank you for advance.
Each store has different return policy.