I was reading the Sandwich Bay Bird Observatory annual report ast night (they are having an open days today and tomorrow,
http://www.sbbot.org.uk) they reckon there was a peak of 5,000 herring gulls roosting in Pegwell bay in December last year. I don't know how that relates to national numbers though.
Wood pigeons are a gourmet delicacy but just as big a pest in the countryside as feral pigeons in the towns, which is bad news for them as that's two good reasons for getting shot.