Another angle would be to pursue this based on the terms of your warranty. Do the terms of your warranty restrict the refund to only be to your original payment method? (this seems ridiculous to me). If so, it is possible you may also be able to challenge this under UK consumer law as an unfair contract term: https://www.which.co.uk/consumer-rights/advice/how-to-compla...
> If the extended warranty document makes it look very difficult for you to claim, or the wording is particularly tricky to understand this could be regarded as an ‘unfair term’.
(disclaimer: i dont live in the UK or know anything about UK consumer law, i'm just some idiot on teh internets, i am not your idiot on teh internets)