Easy. Independence of the Seas from Southampton. Avoid the school holidays though.
Try any one of Royal Caribbean's ships, not sure which one will sail out of Southampton in 2010 though.
Ventura sails out of southampton, it also has more younger people on board, it is a family ship but you don't see that many children as they're too busy in the kids clubs. it's like oceana in some ways but totally different in other ways. we're in our 30s and we loved it.