TTN, theres a small group of people who are still British subjects - they fall between, IIRC, two nationality acts/requirements that turned everyone else into citizens.
fairly small group, and getting smaller - i think its people born in Ireland after a date, from recall, in the 1920's and who have not taken up (as in got a passport) Irish Citizenship.
details fuzzy, and very open to correction - but your chances of meeting anyone who is a British Subject are slim indeed.