The other London ones are the Waterman's Arms in Richmond 2000-2200 19.12 and the Bricklayers' Arms in Putney 1400-1600 22.12
Jeff is pretty welcoming to fellow folkies (it's Hammersmith Morris behind it) and isn't afraid to tell anyone who's a bit too much to bring it back. It obviously helps to be from the Methodist/Chapel tradition this spun off from (CofE West Gallery people outplaced in the Oxford Movement of the 1840s) as you'll know some of the tunes, and better yet to be from the Peak District as you'll know all of them!
The sites are http://www.localcarols.org.uk/intro.php and www.londoncarols.co.uk for the tunes as well.