In my experience most shops (especially larger ones) are well aware of the customer's statutory rights and don't try to shirk their own responsibilities in relation to such matters.If the product is not deemed to be of merchantible quality you are entitled to a repair, refund or credit note. Shops love to tell you it's not their policy. It's not policy, it's law!
In my experience most shops (especially larger ones) are well aware of the customer's statutory rights and don't try to shirk their own responsibilities in relation to such matters.