If you buy something in a shop and it turns to be damaged, broken or faulty in some way, you have a legal right to return the goods and get your money back, as long as they are under guarantee.
If you bought something in a shop and then just change your mind it, you do not have any legal right to return the goods. , many shops have a returns policy which lets you your items back to the shop for any reason and get a refund.
Sometimes shops will only let you exchange the goods something else in the store, rather than you a refund. Or they give you a credit note or voucher to use in their store. This is often the case if you're returning something you bought a sale.
You'll usually to show where and when you bought your goods. You can this with your receipt if you have one.
If you don’t have a receipt and you bought the items using a debit or credit card, you could ask if they will accept a card as proof of purchase.