scotters

Hi everyone.
After I fly into London Heathrow (from San Francisco) I need a cheap one way ticket to Athens. The problem is the two cheap airlines that I know of, Ryanair and Easyjet don't fly out of Heathrow. So my questions are:

1. If I have to fly out of another airport, which is the closest to Heathrow and what is the best method of transportation to get there?

2. Am I missing a cheap flight out of Heathrow that I don't know of?

Thanks everyone!!!!

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