Welcome to Flyertalk and welcome to the BA forum.

There are 2 other threads that will be of interest to you.

https://www.flyertalk.com/forum/brit...3-edition.html

and on 2 October, focusing on cancellations, there were indeed 22 shorthaul cancellations due to the weather, which were fairly obvious at the time. And the other thread is

https://www.flyertalk.com/forum/brit...261-uk261.html

Now this one may actually be a grey area, but usually what BA does is just cancel the shorthauls since there is no added bonus in cancelling a big aircraft - they take up the same airport ATC resources whether big or small. But it is the case that BA needrd to shift flights out of 2 October. I suspect that actually it was a bit of a fusion of circumstances, and weather was one factor in there. Because it was overnight, it seems to me a bit of a stretch to call that extraordinary, but it's not clear cut.

Paging Sigwx for any comments.

As you will see from the second thread, if you are not happy with BA's reply then you can go to CEDR for them to take a look at the paperwork. This can happen if you ask BA to confirm that their answer willl not change.