Cut the sausages into 2.5-cm pieces, then dice the bacon. Heat the oil in a large, heavy frypan and add the sausages and bacon. Fry over moderately high heat for 8 minutes, until the sausage pieces are golden on all sides and the diced bacon is cooked.
Meanwhile, halve, peel and slice the onion. Peel and crush the garlic. Rinse and drain the beans; you don't have to keep them separate from each other.
Remove the sausages and bacon from the pan, drain on paper towels and put aside. Pour away all but 2 tablespoons fat from the frypan. Add the onion and garlic and cook over moderate heat for 5 minutes, until softened.
Stir the tomatoes with their juice into the onion, then add the mixed herbs, mustard and tomato paste. Fill the tomato can one-third full with water, stir well, and add to the mixture. Bring to the boil, stirring, then add the drained beans.
Return the sausages and bacon to the pan and season to taste. Reduce the heat, cover and cook gently for 10 minutes, or until the sausages are cooked through.