Refund period is 28 days.
If you bring the receipt with you then you can get a full refund.
If you don't have the receipt then you can get vouchers to the same value.
If you don't have the receipt then make sure you bring your Matalan card with you so they can check up on the system to prove you bought it.
If you don't have a receipt or your Matalan card they can still check up on the system using your Postcode and Surname.
If you haven't got a receipt and don't have a Matalan card and the muppet on the till used a generic number when you bought it then you might have some trouble.
That's how it worked before I came home tonight anyway.