A lot of Irish stuff on previous answers.
Fro Mags in Kent try to get "What's on Folks" (free at any folk club) - a lot better than "Folk in Kent" which is rather dance and tune oriented.
Monday near London the only choice is "Hazlitt Folk" at Earl's public House Earl Street Maidstone. About 30 miles from London. Email me on McLaw@btinternet.com and I'll send you a "blurb" by return Email.
Sundays (not every week) you should try Richard Matthewman's club at Sturry near Canterbury.
Both the above carry a wide range and are very participative, and you should be abe to hear some at least traditional English song.
Tuesday Dartford club at the Working men's club (15/20 miles out of London) in Dartford is well thought of, but it's a bit American/contemporary acoustic for my taste.