Put the raisins in a small pan and pour over the Cointreau (or orange juice). Simmer over a low heat for 5 minutes; take off the heat and set aside.
Spread the butter thinly on both sides of each slice of bread, then spread one side with marmalade. Slice in half diagonally, then arrange the triangles, slightly overlapping, in a 1.5-litre baking dish. Pour over the raisins and their liquid.
Break the eggs into a bowl and add the 2 egg yolks, caster sugar and orange zest. Beat together. Add the milk and cream and beat until well combined. Pour over the bread, then let sit for 30 minutes.
Preheat the oven to 180ºC, fan 160ºC, gas 4. Sprinkle the demerara sugar over the top of the pudding and bake for 35 minutes, until golden on top, but still slightly wobbly.