The national tourist information website is VisitBritain - VisitBritain is a brand name of the British Tourist Authority

The local tourist offices in towns and cities are often listed under the local government website. These are www."nameoftown".gov.uk  if the town has a county council, e.g www.derbyshire.gov.uk .

Here is a link to Inside United Kingdom : Other UK Websites. It provides easy access to the numerous tourist websites across the UK.