In a bowl mix the lime zest and juice, chilli, oil, soy sauce and honey together. Add the prawns. Cover and leave to marinade in the fridge for 30 minutes.
Just before serving, peel and stone the avocado and cut into slices. Mix with the prawns and toss to coat. Pare the cucumber lengthways into long strips using a potato peeler. Mix with the watercress and rocket and place on a serving plate. Scatter over the prawns and avocado. Spoon over any remaining dressing. Sprinkle over the coriander leaves and sesame seeds. Season with pepper. Serve with extra lime wedges and ciabatta bread.