It's just disgusting how they treat claims tbh. A monkey could give better answers.
As they claim to hold information about the delay, they should provide it. If they refuse to do so, take 'em to court. (MCOL I guess is the first step)
I have yet to come into a position where I have to file a claim against BA, but when the time comes, I'll expect I have to take them all the way to get them to pay up.