Preheat the slow cooker if necessary; see the manufacturer's instructions. Lightly butter 4 metal individual pudding moulds, each 250 ml (8 fl oz), and base-line with a circle of nonstick baking paper. Add 1 tablespoon of golden syrup and ½ tablespoon sugar to the base of each, then add three-quarters of the pineapple and the cherries.
Make the sponge. Put all the ingredients plus the remaining pineapple into a bowl and beat together until smooth.
Spoon the mixture into the pudding moulds. Level the surface with the back of a small spoon, then cover the top of each mould loosely with buttered foil. Stand the moulds in the slow cooker pot, then pour boiling water into the pot to come halfway up the sides of the moulds. Cover with the lid and cook on high for 2–2½ hours or until the sponge is well risen and springs back when pressed with a fingertip.
Remove the foil, loosen the edges of the puddings with a round-bladed knife and turn out into shallow bowls. Peel away the lining paper and serve with hot custard, if liked.