Suggest you "grab" a single cabin on QE2, while she is still in service! Beautiful old ship, with superb crew and a wide range of single cabins.
Fred Olsen ships have single cabins... I enjoyed a cruise in a single on Black Prince this sprin.
The qe2 has single cabins i was on qe2 in august and found the room size more than adequate.
Fred Olsen Line do single cabins but they are still much dearer that when sharing and the cabins are smalle.
Cunard, Princess,P & O and Fred Olsen provide actual single cabins at a cost, normally around a 40-50% premium,but I Know if a cruise is not full some times Olsens will do a late deal.Island cruises really know how to charge, as they only offer double cabins for singles.