Re: A disclosure like this in the US would have landed a prosecution under CFAA
I'd have to look it up (and I cba) to be sure whether this is even a disclosable breach. People seem to have got a funny idea of what data is private, and the bar is set much higher than commonly guessed. Your name and address are not private data in general, although in some cases they can be.
If it is a breach, it's only a very minor one. It's mot booking data, not std treatment appointments. Failing to report it appropriately would be a further breach of regs, but again a minor one.