Place potatoes and water in a large saucepan; cook over medium heat until tender. Meanwhile, in another saucepan, saute onion butter until tender. Stir in the flour, salt, thyme, oregano, celery salt and pepper. Gradually add milk. Bring to a boil; cook and stir for 2 minutes. Add potatoes with cooking liquid; heat through. Add cheese and bacon bits and stir to melt before serving.