A huge amount of statistical data is available from both free sources and published in databases available in the library.
For any statistics found on the web, apply the usual caution. Always check who has published the statistics, and whether they are reliable, accurate and up-to-date.
The UK's largest independent producer of official statistics. The ONS collects statistics on the economy, population and society and also run and publish the census every 10 years. The ONS publishes over 600 releases a year. Statistics are collected into 4 main headings: Business, Industry and Trade (eg. business activity, innovation, different industries); Economy (eg. GDP, inflation, productivity); Employment and the Labour Market (eg. earnings, productivity, unemployment); and People, Population and the Community (eg. culture, education, health, housing, leisure, migration).
This government site collects and publishes official statistics from government departments (eg. Home Office, Dept. for Business, Energy and Industrial Strategy) and public bodies such as the BBCACAS, or Companies House.
The census takes place every 10 years and is a count of all people and households and includes questions on age, ethnicity, employment and religion. It is the most complete source of information about the population that we have.