I don’t know if you’ve already booked, but I’ll add my tuppence worth and say the food on BA can be a bit hit-and miss. I’ve recently done a nine-hour flight, on which we got a rather nice meal two hours after taking off, then nothing for six hours, then two finger sandwiches and a tiny toblerone (which we weren’t allowed to eat!) about an hour before landing.
However if it goes Pete tong you can’t really call how long it’ll be.
Our 747 got cancelled back in 2013 and it was a day before we were on another flight (though we were still in London so we stayed at home for a day), though for a the sake of a day the compensation paid for the flights.