Put the noodles in a bowl, breaking them up a little, and cover with boiling water from the kettle. Leave to soak for 10 mins until tender. Drain, rinse under cold running water, then leave the noodles to drain thoroughly.
In the same bowl, lightly squash the tomatoes – we used the end of a rolling pin. Stir in the fish sauce, lime juice, sugar and diced chilli. Taste for the right balance of sweet, sour and spicy – adjust if necessary.
Toss through the noodles, then add all the remaining ingredients, except the sliced chilli. Season and give everything a good stir, then divide the noodle salad between 6 serving dishes and sprinkle over the chilli before serving.