All open data published by the central UK government:
Including:
GOV.UK Research and Statistics
The general page for the UK Government for all of the internal research and statistics it has.
Office for Budget Responsibility
It is the duty of this office in the UK to examine and report on the sustainability of the public finances. Economic outlook, forecast, trends, monthly public finance report. In particular, Brexit and reports analysis.
The statistics page that focuses on monetary and financial datasets that are relevant to the Bank of England.
Findings are based on rigorous analysis, detailed empirical evidence and in-depth institutional knowledge. IFS seeks to communicate them effectively to a wide range of audiences, and to maximise their impact on policy both directly and by informing public debate.
Office for National Statistics
Data provided by an independent and authorative Office on the UK's public finances.
Free case studies and reports from world companies and associated lesson materials and worksheets
City Business Library has a number of free recommended websites listed under this link.
This includes business start-up, company information, country information, import and export, law and licensing, London research publications, statistics, sustainability and more.