Mix the apple, strawberries, 2 tablespoons sugar and water in a saucepan and place on a gentle heat. Cook until fruit has broken down to desired consistency, then place in the bottom of an oven proof dish.
Mix the oats and flour in a large bowl. Add the butter in small chunks and rub in gently. Stir in the 100g sugar and rub in again.
Sprinkle oats and flour evenly over the fruit and bake for approximately 20 minutes until the fruit starts to bubble up.