Data Sourceslocal ansdell.net
The most useful single source is WikiPedia. It should not be accepted uncritically of course, particularly on contentious topics. Most articles have referenced sources.
A census is taken every ten years. Old ones (typically 100 years ago or earlier) are available through ancestry or genealogy sites. Data is available from even the latest census but it is adjusted so that individual households cannot be identified. Datashine Census, part of the ESRC BODMAS project at UCL. "Datashine Census has a map-based user interface that presents answers to 2011 census questions down to streets.