Tafflyer

That aircraft parts fail is not an extraordinary event. That they fail at less than the estimated or calculated failure interval happens. I believe that not having either replacement part or a replacement aircraft available at your hub airport is bad planning or cost over-optimisation. If I were you, I would reply as such, inform the CAA and push on.

I do not believe in the compensation culture that seems to have become standard in modern society. However, an airline failing to make good it's inadequacies should be strongly opposed. This isn't just a case of the wine in F not being chilled.

That BA stretch their fleet so that replacement aircraft are not available at their hub airport is a commercial decision and not an extraordinary event.