Mix together the tomatoes and 2 tablespoons of the oil in a bowl, then place on a baking sheet. Drizzle over 1 tablespoon of the vinegar, sprinkle with the oregano and sugar and season well. Place in a preheated oven, 160°C (325°F), Gas Mark 3, for 20 minutes or until soft and starting to shrivel. Leave to cool slightly.
Meanwhile, cook the pasta in a large saucepan of salted boiling water according to the pack instructions until al dente. Drain, then cool under cold running water and drain again. Tip into a serving dish and stir through the remaining oil and vinegar.
Gently stir in the cucumber, olives and cooked tomatoes. Toss together and add the feta. Serve sprinkled with extra oregano leaves.