Going on at Game at the moment. Pretty good deal, I took advantage of it:

https://www.game.co.uk/en/m/xbox-liv...credit-2397813

The code is for 3 months, but after inputting it you are prompted to optionally enable recurring billing for an extra free month. After doing so itís easy to disable this via your Microsoft account in the browser. You can do this each time you input a 3 month code.

Additionally, the £10 credit must be spent within 90 days after redeeming or it will expire.