Bring a large pan of water to the boil and add the spaghetti. Meanwhile, heat the oil in a frying pan and cook the pancetta for 8-10 mins until crispy.
Once the pasta is cooked, drain, reserving a little pasta water. Tip the spaghetti back into the pan with the pasta water and add the pancetta with the fat from the pan, the butter, Marmite and cheeses. Use tongs to coat the spaghetti in the sauce and season with a little pepper. Taste and add a little more Marmite , if you like. Serve in bowls with extra Parmesan sprinkled over.