Sounds like a refund. If madison refunded them then madison have accepted it as faulty thus SOGA applies thus refund / replace / repair – your choice.
Q9. Must I accept a credit note instead of a refund?
It depends on why you want to return the goods.
• If you have changed your mind, then the shop doesn’t have to do anything.
• But if the goods are faulty, incorrectly described or not fit for purpose, then you are entitled to your money back (provided you act quickly), and you certainly don’t have to take a credit note
• If you do accept a credit note in these circumstances, watch out, as there may be restrictions on their use.
• If the shop displays a sign stating they only give credit notes instead of refunds, they might be breaking the law and you could report them to Consumer Direct on 08454 04 05 06. Consumers in Northern Ireland should contact Consumer Line on 0845 600 6262.
http://webarchive.nationalarchives.gov.uk/+/http://www.berr.gov.uk/whatwedo/consumers/fact-sheets/page38311.html