Found this on another digital boxset and applied it to the bumper collection of Game of Thrones as whilst it's 6 seasons in the package, it counts as one season. Loophole!
Enter the code via More Purchase Options, then Redeem a gift card or promotion code.
(The code itself can be used on any digital box set)
Note: the code won't apply discount to the product page, but will be seen on the order summary.
If it doesn't work you can get an instant refund!
Offer terms - https://www.amazon.co.uk/b?ie=UTF8&node=10657673031