I use applesauce in baking as an egg replacer (I used to be vegan and DH's grandfather doesn't eat eggs). I've never found it in the UK so I just make my own.
Peel and cut some apples, rinse and drain them, put them in a pan on low-medium heat, cover and cook until soft. The water will come out of the apples as they get hot, so don't add extra. Mash and add sugar and cinnamon to taste.
That satisfies my applesauce cravings and it works for baking.