I read about this on Twitter & FB earlier, and also got the PIN error while trying to update my password on my iPhone, though was able to successfully update it through Safari on my iPad.
Am still concerned about *exactly* what info was exposed, and only got vague answers from BA earlier,

I don’t seem to have any rogue transactions on my credit card, though am a little loathe to go through the hassle of cancelling etc if I don’t need to, esp as I only got a replacement card within the past 2 months.