Preheat the oven to 180C/350F.
In a large, lidded, ovenproof pan, heat the oil and brown the sausages over a medium heat until the have some colour all over. (About 10 minutes.)
Remove the sausages from the pan and put in the bacon pieces, let them brown lightly (about 2 - 3 minutes).
Add in the onions, garlic, parsnips and celery and brown for a further 5 minutes.
Stir in the flour until everything is coated. Add the tomato puree, sage, cider, chicken stock and salt and pepper. Stir well and sit the sausages on top.
Put the lid on and put into the oven for 40 minutes.
Add the apples and cook for a further 5 minutes.
Stir well and serve.