Pre-heat oven to 200C. Cook the macaroni according to packaging instructions.
Mix the cooked macaroni with the bolognese and place in a casserole dish.
Prepare the white sauce: Melt the butter a pot, add the flour and whisk for a few seconds or till flour blends well with the butter. Add the milk half a cup at a time, and whisk vigorously to prevent lumps, keep adding the milk and stirring. The white sauce should be thickened but still runny. If it's too think add a little extra milk.
Pour the white sauce over the macaroni and bolognese mixture in the casserole dish. Put the grated cheese on top and bake in a pre-heated oven till cheese melts and is golden brown. Serve with a salad.