Heathrow or Gatwick?

Geographically, Heathrow works much better since it is essentially between London and the Cotswolds, Gatwick is well south of London.

Without a car, the bus will likely play a part in your trip, if only to get to a train station. Look into the National Express website, you should be able to plan your journey there.

Heathrow is a major transportation hub for Europe. Huge, crowded and more convenient to the Cotswold villages. Are you renting a car? Transport to the Cotswolds is best done by car. About an hour and a half from Heathrow depending on traffic, route and your ability to adjust to driving on the opposite of the road. Can be daunting. Otherwise consider taking a bus to Oxford. An hour ride, pick up you car rental there and proceed to which ever village you've chosen to stay in. I'm certain that others will chime in with other options and opinions about transport to the Cotswolds from Heathrow.

Most trains from Gatwick Airport to Moreton-in-Marsh go via London and require a connection from Victoria station to Paddington station by taxi or Tube. Travel from Heathrow to London by Heathrow Express avoids this issue, since it serves Paddington station and you connect within that station. That reduces driving in a new country while jet-lagged. In Moreton-in-Marsh, you can arrange to meet up with Steve from Value Self Drive ([email protected]), whose car rental office is located a few miles away (see also the intro to Rick's Cotswolds chapter).

I'd go to Heathrow and take a National Express coach from the central bus station there (it's well sign-posted) and if hiring a car, do it at one of the towns the coach takes you to. That will be much easier than coping with the traffic snarl around Heathrow driving on the left in an unfamiliar car. But you can easily get around the Cotswolds by local buses. This website will give you all the links you need.