A Data Guidelines document (last updated November 2011) has been provided with links to help find national, district and local data in the UK, and a section on other countries. Please refer to this, which contains most of the information below, and links to these pages where further detail is available.
Estimates and components of change since 1991, ONS Districts of England
Population Projections ONS projections, districts in a county - England only.
Internal Migration Internal Migration data since mid-1997, districts of England and Wales
Fertility Rates UK national schedules of projected age specific fertility and mortality and Census migration
Mortality Rates UK national schedules of projected age specific fertility and mortality and Census migration
Headship Rates UK district household projections
Economic Activity Rates 2001 Census economic activity data by district & national/ regional ONS projections
What should I use as my base year? (last revised May 2010)
Employment implications and jobs-led forecasts (last revised Feb 2012)
How can I check the quality of my forecast (Last revised Dec 2011)