Combine the oats and milk in a large bowl, and mix well.
Place a couple of slices of peach in the bottom of each of three small glasses. Top each with a couple of spoonfuls of milk-soaked oats, making sure there's a small amount of excess milk for the oats to absorb. Then add another layer of peach slices.
In a small bowl, use a fork to roughly crush the raspberries. Add a dash of maple syrup, and mix well.
Distribute the raspberry 'sauce' between the three glasses, and top each with another layer of oats. Again, there should be a small amount of excess milk, but don't feel you need to add it all if there's too much.
Cover the glasses with cling film, and place in the fridge overnight. They should last for 2-3 days in the fridge. Serve with more fresh raspberries and fresh mint, if desired.