P & O and Ocean Village have self service laundrettes.
Azamara also has a laundry on board. RCI and Celebrity do not. Why would you go on holiday to sit in front of a washing machine.
Sea Princess, Oceana, Thomson Celebration and Thomnson Spirit all have self service laundrie.
Also Sun Princess, on a number of decks, although they are quite small, there will always be a time when you can get your laundry done.