I sailed B2B (back-to-back) on the Sea Princess and will do separate reviews to make for easier reading! The first was 7 days, Spain, Portugal, France and Guernsey.
Due to cost of flying to England, home from New York, I did my air through Princess. I usually do my own, but the cost of sailing single, length of cruise (21 days), I let Princess handle it. Everything went smooth, left O'Hare on time, arrived at Heathrow, did immigration, picked up my bags, walked through green lane for customs and there was a girl from Princess. She explained there were others nearby and we'd walk to the bus together. Very efficient and organized.
Bus ride to Southampton was interesting in that the expressway was jammed so the bus drive took us through the countryside, giving us a little rundown on Windsor along the way, an added treat plus we missed the traffic tie up!