Preheat oven to 350 degrees.
While noodles are cooking, in a microwave-safe bowl, mix soup, 1 1/2 cups of the cheese, mayo and milk and heat through, stirring now and then until cheese is melted. (This could be done in a pan on the stove, instead.)
Chop vegetables and add to the cheese sauce along with the olives. Mix together.
Place half the noodles in the casserole, gently top with the tuna. Pour about half of the cheese sauce over the tuna and noodles. Layer the rest of the noodles over the first layer. Slowly pour the cheese sauce over the top of the casserole, nudging aside the noodles here and there and allowing some of the sauce to seep through.
Cover and bake for about 20 minutes at 350 degrees. Uncover, sprinkle with remaining cheese, and bake for another five to eight minutes until the casserole is thoroughly warmed through and bubbly, and the cheese melted.