If you are outside the 30-day right to reject, you have to give the retailer one opportunity to repair or replace any goods or digital content which are of unsatisfactory quality, unfit for purpose or not as described.
You can state your preference, but the retailer can normally choose whichever would be cheapest or easier for it to do.
If the attempt at a repair or replacement is unsuccessful, you can then claim a refund or a price reduction if you wish to keep the product.
You're entitled to a full or partial refund instead of a repair or replacement if any of the following are true:
- the cost of the repair or replacement is disproportionate to the value of the goods or digital content
- a repair or replacement is impossible
- a repair or replacement would cause you significant inconvenience
- the repair would take an unreasonably long amount of time.
If a repair or replacement is not possible, or the attempt at repair fails, or the first replacement also turns out to be defective, you have a further right to receive a refund of up to 100% of the price you paid, or to reject the goods for a full refund.
https://www.which.co.uk/consumer-rights/regulation/consumer-rights-act