We sailed with P&O on a Christmas cruise on the Arcadia out of Southampton in 2013. It was heavy weather but we are used to bad weather and the whole cruise was a relaxing, enjoyable experience. We'd booked late for unavoidable reasons but it was inconsequential.
My husband was 80 on Christmas Day 2015 and we booked on Ventura to celebrate. True we had to book late again because a family member was terminally ill and subsequently died.
We booked a superior balcony cabin which was not allocated and no explanation was given, P&O couldn't even answer our email. We telephoned customer services to ensure freedom dining and were given that assurance.