I am going back to the US in a few months to visit family. My flight back to Glasgow has a 1 hour layover at heathrow. I have a USA passport and the last time I went through passport control at Heathrow I was in line for over an hour. How am I supposed to make my connecting flight to Glasgow if it takes this long to go through passport control in London. Or is there a different line I have to go to for connections to flights within the UK?