Preheat the oven to 375 degrees F. In a large bowl, mix both cans of Cream of Chicken soup, mayonnaise, and milk. Add diced onion and celery and stir, then fold in the can of drained tuna fish, cooked egg noodles, and a ¼ cup of shredded cheddar cheese. Add salt and pepper to taste.
Pour contents into a 9×13 inch baking dish and place in the oven and cook for 30 minutes. Remove casserole and add remaining shredded cheddar cheese and the crushed potato chips as the final layer. Put back into the oven for the remaining 10 minutes (or until cheese has melted).