You can't, really. Banking legislation does not require them to tell you.

Data laws in EU mandate that a company has to tell you every single entity it has shared your data with, regardless of the sector they operate in.

What you're referring to is that a bank does not require to tell you whether your account is going through specific checks (anti laundering and such).

Banking legislation in the UK does require them to tell you for this kind of breach.

Breach yes, but if they cannot 100% sure identify if your data was given out falsily, then they cannot say. They're not allowed to disclose that they provide your information to LE. So they can only inform you directly if they're 100% sure the specific information request response was sent to false entity. This is very hard to do.

This was a targeted attack towards specific individuals, probably carried out by a state actor or someone after data of very valuable individuals. Unless you're one of those (oligarch, etc), you're probably fine.