Heat oven to 220C/200C fan/gas 7. Use 1 tbsp of the oil to lightly grease a large, shallow roasting tin. Scatter the chips over two-thirds of the tin and line the sausages up on the other third. Cook for 20 mins, then toss the chips around, turn the sausages and return to the oven 10 mins more until the chips are golden and the sausages browned. Push everything together to make room in the tin, then lay the bacon rashers in the space and return to the oven for 10-15 mins or until the bacon fat is crisp and sizzling.
Five mins before the bacon is ready, heat the remaining 1 tbsp of oil in a frying pan and fry the eggs however you like them. Heat the beans in a saucepan or in a microwave.
Split the baps so they are still hinged at one edge. Butter and sauce as you like, split each sausage lengthways and, building from the bottom up, layer the chips, sausage, bacon and egg. Present the bap open for extra sauce and to keep the yolk intact. Serve small pots of beans on the side for dipping and spooning over.