Spray 4 x 250 ml (8 fl oz) ramekins lightly with spray oil. Combine the berries, peaches, orange juice and sugar in a bowl, then divide between the prepared ramekins. Add half the butter to the ramekins.
Put the muesli in a bowl, add the flour and cream and stir until all the muesli is moistened. Sprinkle over the top of the fruit mixture in the ramekins and add the remaining butter.
Stand the ramekins in a shallow roasting tin and bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes until the topping is golden and the fruit bubbling. Serve with cream.