I have a flight at 9:20am from Terminal 1 at Heathrow, and I am interested in taking the Picadilly Line service from King's Cross-St. Pancras to Heathrow T1. How early does this service begin, and how consistent (i.e., frequent) is it throughout the early morning? The earlier the better, as I'm not a happy flier and I like being at the airport far ahead of time. As well, can I get realistic estimates on the time between King's Cross-St. Pancras and Heathrow T1? And any other advice to be proffered would be enormously appreciated. Thanks so much!