We came off a back to back cruise on Iona just over two weeks ago.
We received a letter on the Wednesday in our cabin before the Saturday change over detailing what we needed to do. (Collecting new cruise card from 8.00 am, reminder to finish first cruise bill etc as financially classed as 2 cruises, etc). We were changing cabins, so we had that information. A lot easier for those who were not! However, we could keep our original cabin until the new one was ready (it was available to us from 8.45, so no hanging around).
Yes the laundry was open, but all places to eat or drink closed after breakfast until noon.
We actually left the ship and went into Southampton. Your new card has a gold sticker so you could return on board via the crew entrance and avoid all the new passengers!
We contacted cps and told them, but we did leave a message on the dashboard. As the cruises are different numbers, our keys were actually locked in the safe at the cps pick up shed. So don’t panic if they can’t find your keys, just mention that you are are a back to back passenger. It was soon sorted and only delayed us by 5 minutes tops.
There was no covid testing requirements between cruises for us. But obviously things can change.
Hope you have a fabulous time. It was our first back to back and it won’t be our last.