Whisk together the groundnut oil and green curry paste with half of the lemon juice until smooth. Marinade the prawns in this for at least 15 minutes.
Preheat the grill to hot.
Remove the prawns from the marinade, shaking off any excess and thread three prawns onto each skewer. Grill for 5-7 minutes, turning occasionally to ensure even cooking.
Meanwhile, blanch the peas and mangetout in a large saucepan of salted, boiling water for 1 minute. Drain and toss with the remaining lime juice and the spring onion batons. Re-heat the rice if necessary.
Remove the prawn brochettes when they are pink and tender. Spoon the rice into serving bowls and spoon the vegetables on top. Arrange the brochettes balanced across the rims of the bowls and sprinkle the spring onion on top of them. Serve immediately.