2pm gmt @ 15 degrees per hour = 120degrees west. BST is irrelevant in this case, I arrive at 60 degrees ( give or take a few minutes|)independantly. It should also be considerered that the altitude of the plane has not been given, this would make a significant difference to the times of sunrise and sunset so I am assuming that this additional complication which I believe is a tangential function has been ignored so I'm assuming that the plane is flying at sea level.