Preheat oven to 400f/Mark 6. Heat oil in a large frying pan and fry bacon and sausages for 5 minutes, until browne. Add onion, garlic, sage, and mushrooms, and saute for further 5 minutes. Add wine to pan and boil for 3 minutes. Add tomato puree, stock and Worcestershire sauce, and simmer for 15 minutes.
Boil potatoes for about 15 minutes until soft, drain and mash with butter, cheese and seasoning until smooth and creamy.
Transfer sausage mixture to large ovenproof dish and spoon or pipe mashed potato around edge. Bake in oven for 20 minutes until potato is golden brown. Serve with seasonal vegetables.