Prepare all of the vegetable.
Preheat the oven to 180C/350F/Gas 4
Add the mince to a large non-stick pan and cook on a medium heat until brown all over.
When cooked, transfer to a sieve that is placed over a large plate to drain off the fat. Press the mince firmly with a wooden spoon to drain as much of the fat off as possible. Place to one side.
Wipe out the pan with clean kitchen towel and return to the hob.
Heat the oil on a medium heat then cook the onion, celery, peppers and garlic for around 15 minutes. Stir occasionally until the vegetables are softened and lightly coloured.
Return the mince to the pan. Add the thyme, parsley, oregano, tomato purée and cook for a further 5 minutes.
Add the chopped tomatoes, balsamic vinegar and bay leaves, then bring to the boil.
Reduce the heat and simmer for at least 30 minutes. Season with freshly ground pepper, to own taste preference.
Remove the bay leaves from the mince mixture.
To make the white sauce; mix the cornflour with 2 tablespoons of the milk in a cup. Add an extra clove of chopped garlic if desired.
Add the remainder of the milk and cornflour mixture to a saucepan and heat on a medium heat until the sauce is thick, stirring frequently. It is important to make sure the sauce does not boil over.
Place a layer of meat mixture in the lasagne dish (approximately 35cm x 16 cm), just enough to completely cover the bottom. Then place a layer of lasagne sheets on top of the mince mixture, then cover the lasagne sheets with a thin layer of white sauce. Repeat this layering process of mince, lasagne sheets, and white sauce twice more.
Mix the cheddar cheese and parmesan together then finish the dish by sprinkling the cheese all over the top.
Transfer to the oven and bake for about 45 minutes to 1 hour, until the top is golden-brown and bubbling and the pasta cooked through.
To serve, cut out squares of the lasagne and place onto plates. Serve with a large mixed salad. Feel free to add a couple of tablespoon of your favourite low-fat dressing to your salad.