A few years back I did a penetration test for a hospital, in which a mainframe was in scope (I have some mainframe training from Y2K / tech bubble era, so I almost know what I'm doing in that camp). Because medical students were also working on that mainframe, ample anonymized records were lying around for their studies.

All things said, in my final report were several examples of said anonymized records paired with the actual patient real-life info, obscured only enough that they could verify the result without my report contributing to the problem.

What stood out was how vocal and even cynical they were when I brought up what I had found initially. That is, until I finished the testing and report, complete with a batch script that would automate what I had done manually.

So, I commend these UK adults for recognizing the risks. Everything might be safe as described, but a policy of transparency might help alleviate the trust issue. Allow the public, or at least an expert not connected to the success of the system to know exactly what information is in the records being shared, because sometimes 2 or more disparate data sets can be combined to tell a much bigger story.