Have you already cancelled? If so, then unfortunately there’s nothing else to do but chalk this up to a bitter and expensive lesson.

If not, don’t cancel. As others have said, you may be able to change to an alternate date and route (assuming your personal circumstances would allow). If that isn’t an option, there’s nothing to lose by hedging your bets and keeping the ticket live, on the off-chance a significant schedule change or cancellation of the service by BA makes you eligible for a full refund further down the line.