Cook the noodles according to package instructions, then mix them with the drained tuna, cream of mushroom soup, peas, and half of the cheese. Spread this mixture in a baking dish. In a separate bowl, combine the remaining cheese, breadcrumbs, milk, butter, salt, and pepper. Sprinkle this mixture over the casserole. Bake at 350°F (175°C) for about 25-30 minutes until bubbly and golden on top.