If it was bought in shop and is not faulty then they don't have to refund:
Myth 2. ''If I change my mind, I can get a refund''
Wrong – if the item is not faulty, you have no rights to a refund or exchange unless you buy online (see below). The same applies if goods are the wrong size, unless they are clearly not the size described. Some shops may offer refunds or a credit note as part of their own in-store policies. Returns within 28 days is the policy at most stories, although for the Christmas period many shops will allow items bought in December to be returned as late as January 31.
Source: http://www.telegraph.co.uk/finance/personalfinance/money-saving-tips/11302318/Refused-a-refund-Five-shopping-myths-debunked.html