The UK is a relatively small area, before the growth of no frills airlines flying between the airports in the UK was expensive & not always any quicker than road or rail. Now, budget airlines can make flying between London Luton or Stansted, for example, & regional British & Irish airports cheaper & faster than train or coach.
The Highlands & Islands of Scotland have long been the exception, with short local flights being the main way to reach remote isles & villages.
Below is a list of British airports by region to find the closest for your destination:
Aberdeen Belfast City Belfast International Birmingham International Cardiff International Coventry Edinburgh Glasgow Inverness Leeds Bradford Liverpool John Lennon London City London Gatwick London Heathrow London Luton London Stansted Manchester Newcastle Norwich Nottingham East Midlands Southampton