Done it twice staying in same cabin both times.
First time in Harwich, super simple. They held a meeting the day before to tell us what to expect. On the turnover day they took on an excursion (free) to a nearby town, brought us back to ship. We had an express line and desk to check in again.
Second time a different story. Last April in Southhampton. We were never advised of the meeting, despite several inquiries. Our last inquiry we were told that the meeting already had occurred. We were told that that there would be a separate desk for check in in the terminal when we returned, so we did a self tour to Winchester. Upon return went to the designated desk and it seemed to be in a state of confusion. Ultimately made it back on board to find our sea pass wouldn't open our cabin door, and our beverage package hadn't been loaded onto the card. Three trips to guest service rectified everything. May have been the exception to the process.