How often is a census done in Britain?

Usually every ten years (except during WW2, 1941) - latest census was on Sunday 29 April 2001,

Started in 1801, and now organised through the Office of National Statistics (ONS), part of the UK Statistics Authority.

Public access to the records is restricted by the 100-year rule, meaning that the 1901 Public Census is the latest data set available for public viewing.

Different variations to census data for individual constituent countries of the UK (England, Wales, Scotland, North Ireland etc).

http://www.ons.gov.UK/census/index.HTML