Honestly I think they've lost the general public on this. It was completely different in March because some people (not me, I hasten to add), really believed it would be a 12 week thing to defeat an extremely dangerous virus and the sacrifice would be worth it because then everything would go back to normal. People were generally extremely frightened.
Since then, people have not only realised this is going to be a long term thing, until we have a vaccine, and possibly even longer than that, but they've also realised that it isn't as dangerous as they were originally lead to believe. You only have to look at the data to see that, vulnerabilities or not, the major overwhelming risk factor, beyond anything else, is age. Specifically, being 80 plus.
That's not to say the over eighties don't matter. They obviously do. But for most people altruism towards others they don't know will only go so far.
There's a lot of hyperbole around when people are like "what about diabetics? Or BAME people? etc" but even accounting for those vulnerabilities, the biggest vulnerability by a million miles is age. A 50 year old with diabetes is still overwhelmingly likely to survive the illness.
I'm not debating the rights or wrongs of this. But people know these things now, and they didn't before. The fear simply isn't there like it was in March.
They need to get their test and trace system shit hot, very quickly, because they cannot rely on the general public's compliance any more.