Historical version 4 of Arbat
It's not huge, but seats at least 30.
Accessibility: No step to get in, just a small ridge. Most (possibly all) of the seating is on the same level. Not sure about access to the loos.
OS X co-ord: 452543 OS Y co-ord: 205830 (Latitude: 51.748245 Longitude: -1.238815)