I went into my local Thorntons today and this deal was advertised instore. I have looked online but cant see it so it may just be an in store deal.
With every £12 spend they are giving away free large advent calenders that you can have personalised.
The calenders are for sale instore and online as £6:49 each or 2 for £8.
I stocked up with gifts for christmas and got 2 free advent calenders for my children.
Hope this can be of use to someone :)