Wash and peel the potatoes and cut in to quarters. You may need more or less potatoes depending on your own tastes - I used 4 small and 2 massive! Pop the potatoes in a saucepan of boiling water and simmer until soft enough to mash. Drain the water from the pan and mash the potatoes until creamy. I don't usually add anything to my potatoes but it's up to you if you like to add any butter, milk or cream even!
Quarter the mushrooms and put them in a frying pan with a splash of water and cover with a lid to steam. When they are softened, remove from the heat.
Cook the bacon and sausages under the grill until fully cooked through.
Layer the cooked mushrooms, bacon and sausages (cut in to more manageable pieces) in a large, ovenproof dish.
Cover the bacon, sausages and mushrooms with the two cans of beans (including the tomato sauce). We used Heinz reduced salt and sugar beans here but it's up to you which brand you prefer.
Layer the mashed potato on to the mixture. You want it to be quite thick and I always leave a tiny gap on the edges so the sauce can creep out a little and caramelise! Then cover the potato with a handful (or two!) of grated cheddar cheese.