As Miller has already said Fred Olsen and Saga have single cabins, but when I did a review of Fred Olsen fares I found that generally a Single grade cabin worked out at about sixty percent more than the than the cost of a twin cabin fare.
Contrary to what McCullough says P&O still have some good deals as far as single supplements go, but, and this is a big but, you need to commit as soon as the brochure comes out, and be prepared to cruise in the less popular months (October/November/December, pre Christmas only), this can mean booking eighteen to twenty months in advance, if you can do this the deals are still there.
The only other way is to wait for the offers to become available for late bookings.
There are ships with single cabins eg Fred. Olsen, SAGA which are advertised at specific prices. On the face of it there are no supplements but the price per person is always higher than it would be for a twin/double cabin. Sadly the cruise world is made for couples not singles.
You are definitely right and the supplements seem to be getting higher every year,certainly on P & O.
Single supplements are applied to all cruise lines, so getting a cruise without paying a hefty supplement is not easy. Some cruise lines will offer no single cabin suuplements on the cruises which are not selling well, these are nearly always out of the main holiday season so you have to check out the current offers on the internet or ask a travel agent to do this on your behalf. This means you have to be flexible in your destination and time of travel and will mean a late booking. If you are not able to go on the spur of the moment you are unlikely to avoid paying a single supplement, but the cruise companies at the luxury end of the market often have lower single supplements than the main stream cruise lines. Thus you may be able to travel on a better ship for a similar price you would have to pay on a standard line.
Which cruise lines are the cheapest on single supplements?
I had the dubious experience of travelling on one of Thomson's ships last year paying a supplement for what was shown as a double occupancy cabin. However it must have been the oldest cabin on the ship with the shabbiest fittings. I should have been paid for occupying it. If you pay a supplement then surely you should be entitled to the same standard of cabin as anyone else.I would not recommend this to anyone. When I complained to the customer care staff, they were sympathetic but could not move me as they had their full complement of passengers. Needless to say, when I wrote to Thomsons upon my return, they could not trace my complaint. I would never book a cabin in this way again.
The italian M.S.C. cruise line do truly sell cabins with no single supplement. I have had two cruises with them booked with Readers Offers Ltd. One caribean trip and one from brazil to italy. Huge ships with butlins holiday camp feel! Tables assigned to you for meals two sittings for dinner or free for all buffet on pool deck. Good value trip-drinks expensive and do not expect tranquil ambience.