Personally, I don’t think Johnson and his cronies are deliberately targeting this or that group. They just don’t care. They are scared like everyone else, and are prioritizing the survival of their immediate circles and their social status - i.e. they keep the economy working, keep an appearance of order, and ensure people they care about are “cocooned”, ready to come out when the worst is over. That is their priority. Working-class lives are not priority, that’s all. Health-service capacity woes are relatively unimportant, because people “who matter” will be prioritized anyway.
If they go to full-lockdown, they risk upsetting the existing social order (economy tanks even harder, unemployed people start rioting, etc). That is their worst fear; consider that we’ve had actual riots in London only a few years ago. Saving a bunch of working-class grandpas is clearly not worth the risk of upsetting the current social order, from Johnson’s position. He’d rather have a functioning elite ruling over rubbles, than risk the very own existence of such elite just to save “nobodies”. Add to it a sprinkle of academic Strangeloves, and there you are.
So, _even if_ you ascribe to the current UK government a conspiracy-esque, cold as nails approach to just effectively _murder whole boatloads of older folks_, it doesn't actually make sense: Who would they be so cold as to just casually acquiesce to a solution that results in a lot of death, but they are still human enough to care about the country first and are willing to sacrifice the electoral future of their party?
I'm on 'do not attribute to malice that which can be explained by stupidity', modifying it slightly to 'incompetence'.