Preheat the oven to 200°C, fan 180°C, gas 6. Put the ciabatta pieces on a baking tray and bake for 10 minutes, until crisp and golden.
Meanwhile, heat a frying pan over a medium-high heat, then add the pancetta and cook for 3-4 minutes until crisp and golden. Remove and keep warm. Add the peach slices to the pan and cook for 1 minute each side until golden and slightly softened.
Put half the mint in a small bowl with the lemon zest and juice, red wine vinegar, olive oil, sugar and mustard and whisk together to make the dressing.
Divide the torn mozzarella, salad leaves, remaining mint, ciabatta pieces and peach slices between plates and scatter over the crisp pancetta. Drizzle with the dressing to serve.