If I could do same day change I'd try that, other than that if its touch and go I'd leave it until I got to the airport as, like your family, sometimes you miraculously make it.

If it was a list cause I may tweet BA or phone them on route to advise of the situation and have it recorded that I'm not a couldn't be bothered to show up no show even if contractually its no different, they may proactively offer a solution.