Gently cook the fruit with a few tablespoons of water, half the sugar and mixed spice. When soft, leave to rest in a casserole dish or deep baking tray. Rub margarine into flour and oats. Stir in the remaining spices and sugar. Slowly add the milk to form soft dough. Spoon the dough on top of the fruit and bake for 30 minutes at 190C (gas mark 5). Serve hot with custard or ice cream.