in addition to the above
idk 'walking distance' ... but (and for future readers)

Check Chris Rust's folk music map
https://www.google.com/maps/d/viewer?mid=1d1L8gNDhc6JP84Wyt01-LSEcL_A&ll=51.49298620377847%2C-0.1221855000000005&z=13 
(browser> landscape, not 'maps')

And the UK Ents24 concerts guide set for 5 miles(Sep2017)
https://www.ents24.com/whatson/search/genre/celtic%2Cfolk/near/SE1%207SG/radius/5/from/2017-09-24/to/2017-09-29/order/date 


Timeout
https://www.timeout.com/london/search#/?sort=relevance&q=folk&viewstate=list&page_number=1 

TheSession
https://thesession.org/sessions/nearby?latlon=51.51086044,-0.12217971 

~~~~~~
some related London threads
Clubs
thread.cfm?threadid=50467&messages=31#3841452 

Shanty Session
thread.cfm?threadid=161523