We chose this cruise because we hadn't tried P&O before and having been mainly on older ships we wanted to try Britannia while she was still fairly fresh.
We arrived 10 minutes before our allocated embarkation time and were called almost straight away. By the time we reached our cabin our cases were waiting for us outside the door. Very impressive!
Our cabin was on deck 15 and facing forward. Unfortunately this meant that we had a steel-fronted balcony, but on the positive side it was about 3 x the size of the standard balcony. The deck plans state that this balcony has restricted access while at sea so I had some concerns that it would be locked, but this was not the case. One advantage was that we could see both sides while in port.