HMRC

Information on UK tax, VAT, National Insurance, customs and excise

Companies House

The official UK government register of UK companies

Charity Commission

The official UK government register of UK charities

ACCA

Association of Chartered Certified Accountants

Financial Reporting Council

United Kingdom's independent regulator responsible for promoting confidence in corporate reporting and governance

Chambers of Commerce

The British Chambers of Commerce representing UK business interests around the world

Bank of England

Central Bank of UK. Best source of exchange rates etc.