You need to register your username and password with the Census Registration Service before accessing the data. To do this you need to follow these steps:
This service provides access to and user support for 1971, 1981, 1991, 2001 and 2011 UK census data
Also includes geographic data on UK boundaries : Census boundary datasets can be downloaded for predefined areas or you can create your own using the Boundary Data Selector, which includes environment and historic boundaries. The Postcode Directories provide details of current and historical postcodes along with details of other geographies (e.g. electoral ward, health authority) in which the postcode is located.
Geography and Environment