Most airlines overbook on purpose incase someone decides to cancel they still make profit. Now I remember in the summer flying with Malev to Hungary from Toronto it was an overbooked flight and they first offered $100 cash with a one night stay in a hotel where the next day you fly with KLM. After a few minutes they offered a stay overnight in a hotel and the next day you fly with Air France I beileve it was and it was with a first class upgrade. So if its an airline like BA then you shouldn't worry to much about not making it aboard the worst case scenario is you take a flight the next day with some type of upgrade. Enjoy your trip!
