London isn't actually a cruise port, but is served by the ports of Southhampton, Harwich, and Dover. Together, the port of Southhampton, Harwich, and Dover is the eleventh most departed-from port in the world, departure point of more than two hundred and fifty-five cruises yearly from MSC, Cunard, Princess and more to Europe, the Mediterranean, and the East Coast.
Overall London is rather expensive compared to other ports. See the graph below for the average cost per day by month (Cruises only depart from London between January and December). Sailings scheduled from London during the peak months of winter and summer are somewhat more expensive than the low seasons of spring and fall.