They all do a single person booking but you can pay the price per person plus up to 100%.There are some lines have single cabins Fred Olson being one but it is a bit dearer then a couple sharing,cheapest way to find a friend and book a cabin with them.Try one of the many free phone cruise agents that appear in the week-end papers or try the number at the top of this page,best of luck?
P&O single supplements vary by the cruise so it's probably best to get a brochure to see them all without too much online hassle. Ocean Village have specific grades of cabin where single occupancy can is available. In both instances you get a double cabin for your sole use. The full fare supplement is £450 for a week and £900 for 2 weeks. Given that most fares are discounted by 50% you can basically halve these amounts. The OV website is very good for providing instant online quotes and calculates all these figures for you and advises what cabins are available. Hope this helps.