In the UK we're protected on two levels: firstly the "Distance Selling Regulation" means we have the right to cancel many contracts/purchases made not-in-person within 14 days of delivery.
And secondly, if a good is faulty, not as described, or unfit for purpose then we have a right to a refund under those terms also.
Probably because of these already strong rights, Amazon UK (and most retailers) go beyond that and simply offer a 30 day "no questions asked" return policy in most cases.
I didn't realise until now how much I took it for granted!