2011 Census Data for England and Wales is now available via Neighbourhood Statistics.
The majority of the data is available down to Output Area (OA) level and is also available at 2011 ward level.
There is a new default 2011 Statistical Hierarchy which incorporates changes to OA level geography arising from the 2011 Census. This hierarchy will provide the best coverage for 2011 Census data down to OA level.
Full details of these changes are available from the NDE homepage http://www.neighbourhood.statistics.gov.uk/dissemination/Info.do?page=nde.htm
You may also find the following information useful
2011 Census Geography products for England and Wales
http://www.ons.gov.uk/ons/guide-method/geography/products/census/index.html
National Statistics Postcode products available as free downloads
http://www.ons.gov.uk/ons/guide-method/geography/products/postcode-directories/-nspp-/index.html
Digital Boundaries
http://www.ons.gov.uk/ons/guide-method/geography/products/digital-boundaries/index.html
Names and Codes Look-ups
http://www.ons.gov.uk/ons/guide-method/geography/products/names--codes-and-look-ups/index.html
2011 Census data for Scotland is available from here http://www.scotlandscensus.gov.uk/en/ while data for Northern Ireland is available from here http://www.nisra.gov.uk/Census/2011_results_key_statistics.html