Preheat the oven to 200 C / Gas mark 6. Lightly grease two baking trays.
Place the flour and baking powder in a large bowl; add the margarine and rub in with fingertips until mixture resembles fine breadcrumbs. Stir in sugar and fruit; add the egg and 1 tablespoon milk and mix to a stiff dough. If dry, add a little more milk.
Using 2 teaspoons, shape the mixture into about 12 rough mounds; place on prepared baking sheets. Sprinkle with demerara sugar.
Bake in the preheated oven until pale golden brown at the edges, about 15 minutes. Cool on a wire rack.