Preheat the oven to Gas Mark 4, 180ºC (350ºF). Line a muffin tin with deep paper cases. Melt the butter in a small pan or in the microwave. Remove from the heat.
Sift the plain flour, baking powder, bread soda and salt into a bowl. Stir in the wholemeal flour. Beat together the milk, yoghurt, eggs, warm melted butter and orange rind. Make a well in the dried ingredients and stir in this mixture along with the marmalade.
Spoon the mixture equally into the paper cases and bake for 20-25 minutes until well risen and golden brown. Leave to cool for five minutes, then serve warm with a pot of hot coffee.