In a large Dutch oven, saute onion and celery in butter for 5 minutes. Add potatoes and water. Bring to a boil. Reduce heat; cover and simmer for 15 minutes or until potatoes are tender., Stir in 2 cups milk, bouillon, salt and pepper. Combine flour and remaining milk until smooth; gradually stir into soup. Bring to a boil; cook and stir for 2 minutes or until thickened. Reduce heat. Add cheese and bacon; stir until cheese is melted.