Mix the fruit and demerara together in a small bowl or large mug and pour the rum over it to coat all the fruit. Mix the fruit and sugar around in the rum then cover and leave in the fridge for 24 hours.
Preheat oven to 180°C.
Butter all the bread you have on one side and put aside.
Slowly mix 150g white cane sugar in a bowl with 4 eggs, added slowly. Also add 2 drops of vanilla extract.
Whisk slowly until smooth and creamy, then continue to add while slowly adding the cream and the milk.
Layer the bread in the bottom of a large ovenproof dish and then sprinkle the soaked fruit over this layer. Add another layer of bread, and repeat the process until you run out of bread and fruit.
Pour over the vanilla custard and allow to stand for 15-20 minutes to allow the bread to soak up all the custard. If you have any rum and sugar remaining in the fruit bowl pour this over the top of the pudding after 15-20 minutes of standing.
Place in a bain marie in the oven and cook for around thirty minutes until it is golden brown and slighty crispy on top.