Cook haddock, cool, remove skin and flake - set aside. Cook bacon in oil until cooked but not crisp - remove and add to haddock. Add butter and onion to same pan and cook until tender - remove and add to haddock. Mix flour and mustard powder and stir into pan drippings, cook one minute. Gradually stir in milk to make a smooth white sauce and mix gently. Stir in parsley. Meanwhile cook macaroni as directed on packet until al dente - drain. Mix cooked macaroni and haddock mixture. Turn into a greased ovenproof dish. Sprinkle with cheese and bake in a preheated oven of 180*C for about 20 minutes.