Many accurate 1921 census transcriptions have already been added to the pub history site, including London, and parts of Middlesex. If you can contribute to the site, send me some details to Kevan, along with some description of the specific property.
This is a listing from the Public Houses section of the UK Northern and Southern London Post Office Directory in 1896; This is one of the earlier London Suburbs directories that lists Pubs and street addresses as London instead of the local county.
London Northern suburbs
London Southern suburbs