My vote would also be for Celebrity. Galaxy - Eastern Med sailing from Civitevechio was fab last year. Keep saving cos' once you've been on a cruise you'll be bitten!! Have a great time. Martin.
Might be worth checking out the itenaries for P & O Cruise ships Arcadia and Artemis as they are adults only no kids. I think the Acadia is leaving from Southampton so no great travel distance from Manchester.
I can also recommend Azamara, more class than P&O and with the quality and the feeling of a manor house at sea, brilliant food and great atmosphere. A terrific choice for a special occasion.
Why not look through the Berlitz Guide at the other cruise ships too? regards Ida .
My vote would be for Celebrity or Azamara. P&O has the atmosphere of a 3* Bournemouth hotel in November...IMHO.