If you’re looking to buy something from Amazon, move quickly and buy a £5 Amazon Gift Certificate over at Bespoke Offers and you’ll get another free, effectively doubling your money.
This one isn’t likely to last too long, especially at this time of year, so it you want to use this one, don’t hang around too long! It states it's available until December 18th but I'd imagine the vouchers available may sell out before then. You can use your voucher from today (16th) and it's valid until December 28th.
Edit : Looks like Bespoke are so busy processing orders that there may be a delay of up to an hour between purchasing your voucher and it being added to your account.
Thanks to nefertiti6969 @ HUKD!