Preheat oven to 200°C/400°F/Gas 6. Lightly grease an 18cm/7" sandwich tin or a plain flat baking sheet. Sieve the flour and caster sugar into a mixing bowl. Rub in the margarine and stir in the sultanas. Beat the egg and milk together and add sufficient to the dry ingredients and mix to a soft dough. Turn onto a floured surface and roll in the flour. Shape into a round shape and fit into the sandwich tin or put onto the flat baking sheet. Score or cut the top into 8 sections. Brush the top with the beaten egg. Bake for approx. 15 minutes until well risen and golden brown. Serve hot or cold with butter or with spread of your choice.