My enquiries are P & O charge a single supplement between 50% and 90% which added to the basic fare equates to two people sharing. They only allocated a small number of twin cabins for single occupancy. Once these have been taken they then charge cabins at twin rates. QE2 have limited single cabins but it is old. Stick to a modern, clean ship.
Some cruise lines like Fred Olsen, Spirit of Adventure, Voyages of Discovery have single cabins which are tailored for singles. However, most cruiselines you have to pay a suppliment so you may aswell take friend with you as it costs as much if not mort.
I am aware that P&O do single cabins in the JA to OH on Oceana but there is a single supplment which you need to pay. The single supplement varies from cruise to cruise. You will need to speak to you travel agent for the exact supplement that you will need to pay.
There are many Cruise lines that cater for Single Travellers depending on itinerary, ship and obviously availability. Some cruise lines will charge a supplement for for selling a double cabin for sole occupancy similar to a hotel. best thing to do is talk to your travel agaent and discuss the best ship and itinerary that will suit you best.
Yes the QE2 has single cabins.