http://www.folklondon.co.uk/

and their venues page http://www.folklondon.co.uk/venues.html

I would expect something to be on @ C# house. https://www.cecilsharphouse.org/csh-whats-on

very sketchy on Dance. There is a Knees Up Cecil Sharp Fri Monthly and Primrose Hill Community Centre host on Bouch 2nd Fri - French/European dancing and if you can play - join the band. The night I went the band was 4 hurdy gurdies (and Chris Shaw left his in its case!). & I couldn't see: George Inn?, 77 Borough High Street, London, SE1 1NH 1st Monday listed (mainly French) session and maybe some dancing.