There was some talk up-thread about a Wiki, which might be useful for those affected/concerned. I'm too much of a noob around here to start/edit one, but as well as suggested actions/contact details for major financial institutions, perhaps some post-breach advice for various circumstances.
A good starting point, and continuing useful resource is the website
https://haveibeenpwned.com This site has data of 304 website breaches, and allows you to search by your email address to see if you have been 'pwned' (translation: a victim of a breach). Fortunately I was not affected by this BA breach, so I'm not clear if this site has details yet, and I suspect not. The
Wikipedia article gives technical details on how the site works (and why) for those so inclined.