The Supply of Extended Warranties on Domestic Electrical Goods Order 2005 gives you the right to cancel a warranty if the duration of that warranty is for more than a year.
If you cancel within 45 days of taking out the warranty, and you haven't made a claim on it, you must be given a full refund.
If you've made a claim or it's beyond 45 days, you must be given a pro-rata (partial) refund.
These cancellation rights don't apply to an insurance-backed warranty that's bought at a distance - such as online.
If the retailer you bought the warranty from refuses to give you a refund, quote the Supply of Extended Warranties on Domestic Electrical Goods Order and let them know you have a legal right to a full refund.
The Regulations don't set out how quickly the refund should be made, so you'll need to set a reasonable timeframe for the refund - say 14 days.
If 45 days have passed, you would still be entitled to ask for a pro-rata refund.
This means you would need to work out what proportion of the warranty you have had the benefit of and ask the warranty provider to refund to you the balance.
If you've made a claim on the warranty you would still be entitled to a pro-rata refund unless it was a term of the warranty that the warranty ended on making a claim.