I understand your question. However from a commercial point of view they must draw a line in the sand somewhere and the 1st of september is as likley as the 2nd..

If Ba and other carriers are going to fly and provide a service they have to expect people that have booked to honour their half of the contract at some point. We need them to fly and they need us to pay for the tickets. They cant set a schedule if we keep kicking the can down the road.

And to answer your question. The answers are you claim on your insurance or you pay to swap dates.

Believe me its not something I would be happy about if I had a flight booked to Japan on the 1st of September but I knew this point would come at sometime and for the sake of the airline and future schedules september the first seems reasonable.