Widerrufsrecht
Customers are entitled to a refund, repair, or replacement if goods are faulty, not as described, or unfit for purpose. For faulty goods, customers generally have a short-term right to reject within 30 days, and after that you may usually offer a repair or replacement first. GOV.UK also says you must repair or replace an item returned within 6 months, unless you can prove it was not faulty when bought.
For online, phone, mail-order, or other distance sales, customers usually have 14 days after receiving goods to cancel, then another 14 days to return the goods. We normally refund within 14 days of receiving the goods back or receiving proof they were sent.