I have friends and colleagues in BAH, and have visited in the last couple of weeks, so I am reasonably close to the situation, but by no means an expert.

I don't know the extent that BA chose to reschedule or were under pressure to do so by the UK embassy in BAH and the FCO. It's fairly clear that the curfew has not prevented travel to and from the airport during the night in any practical sense. However, the UK embassy has a duty of care to UK nationals in country and has understandably discouraged people from taking undue risks.

IMHO, unless BA can claim they were forced to make the schedule change, then it was their own choice to do so and they should look after people who have been inconvenienced as a consequence.