I, too, have read those posts by the lad. One way to go: the Cunard site gives information about joining the line. Check it out, whatever your country. What with the high turnover on staff, I'd think the line would always want good help. Remember WHY they call it work.....if you go on as a waitress, you will WORK. In ports, you will have hours off and be able to see much, if you're not too tired.
Cunard now being a name-brand, run by new people running many ships, with the staff quite interchangeable ship to ship, I'd imagine there are several low-level jobs available at once..after a bit of training. Once you're on and know the drill, you may find several areas on ship to interest you and you might be able to move about.
Look into the main personnel office of the line. Good luck. Post and let us know how you do.