Preheat the slow cooker if necessary; see the manufacturer's instructions. Lightly butter a 1.2 litre (2 pint) pudding basin and base-line with a circle of nonstick baking paper, checking first that it will fit in the slow cooker pot. Spoon the golden syrup and 2 tablespoons of the marmalade into the basin.
Put the flour, suet, sugar and ginger in a bowl and mix together. Add the remaining marmalade, orange rind and juice, the eggs and milk and beat until smooth. Spoon the mixture into the basin, spread it level and cover the top with buttered foil.
Lower the basin into the slow cooker pot and pour boiling water into the pot to come halfway up the sides of the basin. Cover with the lid and cook on high for 3–3½ hours or until the pudding is well risen and feels firm and dry when the top is pressed with a fingertip.
Lift the basin out of the slow cooker pot using a tea towel and remove the foil. Loosen the edge of the pudding with a knife, turn out on to a plate and peel off the lining paper. Serve scoops of the pudding in bowls with custard or vanilla ice cream.