Just found this deal while searching for my brother.
The Gears of War bundle is currently £299.99 but a promotion allows you to add Halo 5 Guardians which knocks a further £15 off, bringing it down to £284.99.
Seemed a good deal with 2 good games.
Worth noting that there is also the same deal with Fallout 4 for £299.99 if you would prefer that game over Halo 5.
Also: £10 argos voucher for spending over £100. Thanks