I am going from Seattle to Athens with a 5 hour connection at Heathrow in between. I have heard Heathrow is a very large and complex airport. Does anyone know how the connection process works there? How soon can I find out what terminal I will need to go, to catch my flight to Athens? My layover is 5 hrs so should I shop around at the different terminals or stay put at mine and get a meal there? Any tips would be great!