Hi John, firstly Congratulations to you both :) I'm sure you will enjoy this cruise, my wife and myself have done it and had a great time. Boarding in Southampton is really good, beats Airports anytime plus you will be allowed onboard even before your cabin is ready. If possible try to arrive at the terminal about 1230hrs no matter what boarding time P&O gave you, forget your luggage they are pretty slick with that, it just turns up in your cabin. Enjoy it mate :)