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.
The listing of beer retailers in 1914 in the many trade directories is a useful guide to the London street directories. Many of these beer retailers / publicans are just off licences. Others are the pre-requisite of the modern Pub as we know it today.
Here are a few (about a thousand publicans). They are all listed by address only, but you may find a 'pub sign name' has been added in the census, which makes this more appealing.