Call Of Duty: Advanced Warfare is out now on Xbox One and Xbox 360, containing four new multiplayer maps, Exo Zombies and a directed energy assault rifle for £11.59.
Or less, if you stock up on some cheap Xbox Live credit!
Right now the most competitive deals can be found on CDKeys, who'll part with £15 of Xbox Live credit for only £13.29 using the Facebook voucher code. That means that you'll effectively buy the Havoc DLC for £10.26, while still having £3.41 left over to put towards your next Xbox Live purchase.
However, if you want to think bigger, you can alternatively get £50 Xbox Live credit for £43.60 with the Facebook voucher code, which works out the best in terms of credit/£ especially if you're thinking of getting the season pass. Doing it this way means that the four DLC packs work out at £7.63 each by my reckoning!
Note that both of these options require you to spend more than £11.59 - the saving comes in the long-term.