Heat the oil in a large pan. Sizzle the sausages for about 6 mins, turning occasionally, until brown on all sides, then remove to a plate. Tip the carrots and onions into the pan, then cook for 8 mins, stirring occasionally, until the onions are soft. Add the vinegar to the pan, then stir in the drained beans. Pour over the stock, nestle the sausages in with the beans, then simmer everything for 10 mins.