For the dressing:
1. Cook the pasta in a large sauce pan of boiling salted water, following packet directions or until al dente. Refresh under cold water and drain.
2. Meanwhile, for dressing, whisk together the mayonnaise, tomato sauce, juice and Worcestershire sauce in a large bowl.
3. Arrange the pasta, prawns, cucumber, avocado, saladmix, chives, mint and dill on a platter. Season. Drizzle with the dressing and scatter with extra dill. Serve with lemon wedges, if you like.