Hmm, don't think so. If the goods fail to comply with Sale of Goods Act, "of merchantable quality, fit for the purpose etc" think they have to give a refund. Exchange or credit note is their goodwill gesture if you change your mind about soemthing.
If you mean you want to take it back if it doesn't match? Then, no they are not obliged to offer any refund if you just change your mind (don't have to exchange or give credit note either) They only have to refund if the item is faulty.
Yes, it correct unless the goods are faulty, damaged, not as described/fit for purpose. Simply changing your mind because it doesn't suit doesn't oblige them to give you a refund or exchange but in practice many retailers do out of goodwill but you may still need a proof of purchase (receipt, credit card statement etc).