I don't know if it's P&O's intention to target only British customers, but that certainly seems to be the case with the Arcadia. This ship gives almost no concessions to international travelers who would likely find the food choices/dress codes, etc. entirely attuned to British tastes. If this is the intention, the formula succeeds for I would say that most of our fellow cruisers were British, many of them regular P&O/Arcadia passengers - and they all love it!
But my husband and I are not British and we are experienced cruisers. P&O is the fifth cruise line we have sailed with and it was, by far, the least of an otherwise very good bunch. I won't say "worst" as that implies we were miserable, which we were not, but I would be very reluctant to sail with P&O again.
Good points: the ship had come from refit and seemed fresh and clean with new curtains, carpets (badly fuzzing) and general sprucing up (so we were told). The public areas are well done. We had a deluxe balcony cabin which was comfortable and as spacious as these things go, with new beds, good storage, flat screen TV + excellent cabin steward. So all fine there. While it was a nice touch to have the use of binoculars and a world atlas, I would have appreciated the use of robes much more. No robes.