Heat the oil in a heavy based pan. Add the onion, carrot and celery. Fry gently for 5 minutes or until beginning to soften. Add the venison, turn up the heat and cook for a further 2-3 minutes, stirring to break up the lumps, until lightly browned.
Add the stock, wine, canned tomatoes, tomato paste. Stir well, bring to the boil, cover and simmer for 40 minutes until the meat is tender and the sauce is thickened and reduced. Season.
Mix together the white sauce, crème fraiche and Cheddar cheese.
Preheat the oven to 170C/380F/Gas Mark 5.
Lightly oil an oblong ovenproof dish. Spread about one third of the sauce over the base. Cover with 3-4 lasagne sheets, trying not to overlap them too much. Spread with about one third of the white sauce and sprinkle with Parmesan cheese. Then add a layer of meat sauce, spreading evenly.
Repeat the layers twice more, finishing with the sauce and Parmesan cheese. Bake for 30-35 minutes until browned and bubbling around the edges.