Just a word of warning. If you bid for an upgrade and are successful check out your new cabin position before paying for it. We had a balcony cabin on A deck Britannia. I thought because it was under the overhang that I would try to get a better one. We were successful and were allocated G731. It was at the aft of the ship, did some research and mentioned might get some soot but nothing else. It has to be the worst cabin on Brittania right above the live lounge, all you can here is boom, boom, boom till the early hours of the morning. No chance of an early night. So do your research and don't end up like us. Glad to get home for a good night's sleep.
Ian