Cook pasta in a large pot of boiling salted water as directed on packet, until just tender. Drain and set aside.
Heat olive oil in a small saucepan. Add spring onions and cook, stirring occasionally, 2 or 3 minutes. Stir in garlic and cook for 2 minutes. Add pasta, tomatoes, salt and pepper. Cook over low heat to warm through. Stir in mozzarella and Parmesan cheese. Coarsely tear basil leaves in halves or thirds; add to pasta with olives and serve immediately.