Cook macaroni in boiling salted water until "al dente". Approximately 5-6 minutes. Meanwhile, in a small saucepan, melt butter. Stir in flour, salt, mustard, pepper and hot pepper sauce. Cook and stir until smooth. Drain macaroni; combine with butter mixture in a large bowl and mix well. Stir in milk and 2.5 cups of cheese. Pour into an ungreased 2.5 quart baking dish. Cover and bake at 180ºC or 30 minutes or until bubbly. Sprinkle with remaining cheese; let stand 5 minutes before serving.