The UK approach here is basically just accepting that a majority of the population is going to get infected by design. That's fine. It might even be true. (It obviously will be if you don't do anything to stop it, but even in aggressive lockdowns I mean)
But it benefits nobody to have it spread quicker. Maybe life in the UK gets back to normal a little faster for people who are not at-risk or aren't treated at risk but we live in a very global society and if everyone else is locked down then it's hard to see much benefit for the UK itself.
And your parents and the portion of the population who are most vulnerable are more at risk.
An imperfect defense is better than not even trying.
Amongst other problems, the term "expert" is ill defined (see discussion above about mathematicians) and there's always value in contrarianism for people who aren't directly making decisions. If they're wrong nobody will remember and there's nearly no reputational impact. If they're right, they can win fame and glory.
I don't know enough to say that the UK strategy is correct (i hope it is - i live here, and more importantly, so do my parents). But i think the situation isn't cut and dried.
Hopefully, we will get a lot more detail in the next few days, and then the real experts can come to a consensus.