Ican think of several folk clubs in London I used to go to but ar enow demised:

Richmond Folk CLub - Bull & Bush
Hammersmith Folk Club (my first) Kings Head, Fulham and before my time Prince Of Wales
Kingston Folk Club - Cricketers
Cityfolk - Various locations along Borough High Street
Central Folk Club - Various Locatins in and around Tottenham Court Road
Capital Folk CLub - Various locations around Covent Garden and Marylebone
Dingals Folk CLub - next to the Post Office Tower
Ealing/Chiswick Folk CLub - Ealing Conservative CLub/Packhorse and Talbit
Wellington Folk CLub/Parsons Nose Folk CLub - Fulham Broadway and The Alma Parsons Green
Ealing Folk and Blues Club - The Castle

Thta's all I can recall at the moment