So I called their help advice line 2 8028 0534. Went to the UK. Chap said to call IDCare, who were 'looking after things'; gave a number starting with 2 (I corrected him and said it should be 02 outside of NSW).
I rang ID Care - 02 8xx_x number, so it too is offshore - Brit accent. Rather strange conversation. Didn't sound like he had been briefed, but then sorted it out. To cut a long story short, they were reassuring that nothing to worry about. Info leaked can't be used for identity theft. I challenged re hacker with data accessing third party accounts. No. When I summarised the call as "so its a case of 'don't worry, be happy' " ? He said 'That's right'.
I did note that in these things, what's said to have been disclosed early wasn't the end of it, and he agreed. Then gave me a client number 'so if I call back' ....
Ye Gods.