In a large frying pan, fry the sausages (whole or sliced) until brown.
Add the taco sauce and stock, bring to the boil then let simmer.
In another pot boil the macaroni till al dente and set aside.
In a saucepan melt the butter, remove from the heat and add the flour, whisking until mixed. Slowly add the milk whisking all the time. Place milk mixture back onto the stove and whisk slowly till it thickens then add salt to taste.
Place the macaroni in a casserole dish, pour over the sausages and sauce. Mix the sauce through.
Pour over the bechamel sauce, making sure all the macaroni is covered. Sprinkle over the grated cheese and place under the grill until the cheese is golden.