In case anyone else is looking for one, I just wanted to recommend Rooftop Post as somewhere to get lovely letters from Santa from.
I spent hours last year searching for somewhere good after being disappointed in the past - but not having the time to make my own - and plumped for one of their DIY letters (where you write the text yourself) This year we've got one of their pre-written stories and it's wonderful.
The letter is beautifully printed, tied with a ribbon and filled with glitter and confetti - DS is going to be so excited when he opens it on Christmas morning :)