You should seriously consider booking a voyage on either QE2 or Queen Mary 2 -- they both have excellent collections in their libraries that deal with the history of the Cunard Line. At the same time, if you did book a voyage, you could conduct oral interviews with senior officers -- great as a piece of field research. Also, take a look at Stephen Fox's book "Transatlantic" (excellent on line's history & development). Also, send an email to the webmaster of the World Ship Society. He is a Cunard historian (see website for email -
www.worldshipny.com). Authors John Maxtone Graham and Frank Braynard are well regarded for their scholarship as maritime historians. Bill Miller is also knowledgeable in a general sort of way.
I assume you are looking at marketing, but you cannot divorce marketing from pure martime/ oceanliner history which is what Cunard (read Carnival) is selling. Queen Mary 2 is, quite sadly, a prefabricated theme park of the golden age of transatlantic travel which Cunard/Carnival exploits, very obviously on the Queen Mary 2 and in its brochures. QE2 is the old real blueblood, the last surviving link to the age that Cunard is tapping into. QE2 is acutally an interesting story in herself in terms of how she has evolved and has been marketed.
Sounds like a very interesting dissertation. Good luck & let me know through the messageboard if you need more ideas or direction.