Are there any sessions (anything but all-Irish or singer-songwriter) in London on Friday or Saturday nights? I'll be there on the weekend of 13th-15th March.

This from the Folk and Roots listings looks the most promising, despite being in a ghastly part of town:

A new weekly session with a mixture of English, Irish and Scottish on Sunday evenings at "Kitsons" on Devons Road E3 (Bromley by Bow Tube) 0207 9872356

but the phone number doesn't work.

One that had a bit of klezmer would be nice.