P&O do show there disabled cabins marked. Not all ships have disabled cabins but you can buy a book' Berlitz Complete Guide To Cruising and Crusie Ships 2007' in which all ships are listed and it shows whether or not they have any disabled cabins. You could then speak to your travel agent or the company direct.
Hi try norwegian cruise lines, they have a diagram of each floor and a choice of room no. .each floor has a key and shows wheelchair accessible rooms.friends of mine have just done royal carribean transatlantic, they said the wheelchair access and their treatment and help was fantastic.hope this helps su.