Pre-heat oven to 200°C/Fan 180°C/Gas 6. Cook the pasta in slightly salted water, reducing the cook time stated on the pack by 5 minutes. Add the broccoli about 3 minutes before the end of the reduced cook time. Reserve half a mug of the hot water before draining and put the pasta into an oven-proof dish.
Melt butter in a pan, stir in flour, add the milk and continue stirring until the sauce is smooth and thick. Cook for at least 4/5 minutes. Stir in the Cheddar until melted and then add the Sweet Mustard Ketchup and the reserved pasta water. Season to taste. Pour the sauce over the cooked, drained pasta and broccoli, sprinkle with the breadcrumbs and bake in the oven for 25-30 minutes until bubbling, crisp and golden.