I've found that often it's just as inexpensive to go directly to the airlines' websites versus travelocity.com, orbitz.com, etc. As much as they'd like to believe, they ain't always a bargain. With the airlines, you'll get a bit more consideration if there are screw-ups.

Departures from US to UK are pretty much limited from either Atlanta or Newark. And since it's been several years since I've departed from Atlanta, I'm not certain what's currently available there.

If flying from Newark to Edinburgh (on Continental), get to Newark with lotsa time to spare. Arrival flights are chronically late.

Slan,
steve