I have been on the Oceana twice: the Oceana Atlantic crossing in November 2003 from Southampton to the Caribbean and then again in December 2004 on a Caribbean cruise from Barbados. It's a lovely ship and you can find lots of information about it on the P&O website www.pocruises.com
. You could also try uk.groups.yahoo.com/group/welovecruising where most of the P&O fans seem to congregate
P&O is an excellent cruiseline, I would say on a par with Princess. It's probably 99% British people. Food excellent. Entertainment better than Celebrity or Princess which are the only other companies I can compare with. The cabins are also of the same standard.
Regarding the balconies, they are not fully enclosed - just a railing to stop you falling overboard.
The only complaint I had last year was that they started putting up Christmas decorations during our cruise but not for us - they were for the next cruise. On the last night in Barbados the ship was totally dead, even the bar on deck was shut - it was as if they couldn't wait to get rid of us so that they could welcome their Christmas cruisers on board!
I'm a little bored with P&O at the moment and want to try different cruiselines such as Costa, Norwegian and perhaps Holland America.
I'm sure you'll have a wonderful time - you can't really go wrong with P&O.