Actually, none of those cruise lines are British owned, even if they are largely marketed to British holidaymakers they are all largely owned by American corporations and based on the American cruising model which now seems to dominate the market. They are all 'flagged out' even if P&O still flies the red ensign by special permission. MSC appears to be wholly owned by an Italian shipping company so perhaps expect a more Mediterranean laidback atmosphere rather than American slickness? Sorry I can't be of more help about the details but a friend in the trade says that they are a decent company.

SM