Cook the pasta and, about 4-5 minutes before it is ready, add the broccoli florets. The broccoli should be softened when the pasta is cooked. Meanwhile, fry the bacon in a frying pan. Also meanwhile (!), make the cheese sauce by melting the butter, adding the flour to get a paste, adding the milk while stirring continually and heating, adding the cheese (grated or crumbled) and then stirring in the mustard and seasoning. Add the bacon to the sauce.
Grease a dish with butter and add breadcrumbs. Mix up the pasta and broccoli and then pour into the dish. Pour over the bacon and cheese sauce and then mix up with a spoon. Add some grated parmesan and breadcrumbs on the top. Put in 180C oven at the top for 5-10 minutes, then grill the top for a further 3-5 minutes. Serve after letting cool for 10 minutes or so.