Jump:
Ordnance Survey – Great Britain's national mapping agency
In October 2007 we created the ‘effective’ England and Wales Westminster (parliamentary) constituency boundaries, which accompanied the October 2007 Boundary-Line release.
Boundary-Line is a specialist 1:10 000 scale boundaries dataset. It contains all levels of electoral and administrative boundaries, from district, wards and civil parishes (or communities) up to parliamentary, assembly and European constituencies.
The information is represented as vector digital data.
The boundary information is updated twice a year, in May and October. The May release contains the boundaries that become live in the first week of May, in the year of release. The October release contains the May boundaries plus additional information. Customers can choose either May or October releases.

Take a look at how Boundary-Line data might appear in a GIS by launching our product viewer.
Census Output Areas are the definitive polygon geography for the 2001 Census results. Created by the ONS for England and Wales and the General Register Office for Scotland (GROS), their purpose is to link census data to geographical areas.
The data for England and Wales are available by direct request from ONS by email to census.customerservices@ons.gov.uk, and the data for Scotland are available from GROS, email customer@gro-scotland.gov.uk