I am coming from Edinburgh, headed for the United States. I have a 6 hour layover at Heathrow. How easy is it to leave the airport? What checkpoints do I need to go through to get out. Also, how soon should I get back before my flight since it's such a busy airport? Thanks!

sorry -- but your really don't have time to do anything much. You could go for an Indian meal off airport or something like that. But if you land in the morning,probably not what you have in mind. You'd have to keep your carry-on's w/ you. Otherwise you'll have to queue to stow/collect them from Left Luggage.

You don't have time to make it into London and back and see/do anything. You <i>could</i> maybe catch a cab to Windsor (same carry-on issue though). You'd have about and hour free in Windsor.

Are you sure you want to leave the airport?? There are first/business lounges readily available for reasonable prices or regular passenger lounges. google LHR lounges.. Due to the crowds at security/luggage/check in you may run into difficulty. There are also many shops to cruise and/or buy stuff in. You may be able to get into your airline lounge on a day pass...worth trying..I personally wouldn't leave...Have a good trip!!!

Lots to do at LHR I never get boared there many shops little
to do in the area around the airport security in/out very
crowded.Personally would relax enjoy activities IN the airport.Great Starbucks there many nice lounges also check with your carrier for admission.Have fun!

You will probably be switching from Terminal 1 to Terminal 5
and that will take approx. 90 min. according to the Heathrow
website.

After immigration and customs and finding your way to your
next departure you will probably be down to 4 hours and that
just isn't enough time to go anywhere from the airport.

Shop/eat/gawk - the time will go quickly.

If shopping is not your thing, treat yourself to one of the aiport lounges with a day pass and have a nice meal.
I wouldn't attempt to leave that airport.