But personally find the whole class set up pretty unfortunate really (and its impact largely underestimated).
The "middle class" is quite a recent invention; it arrived with the Industrial Revolution, and is largely Victorian in origin. The growth of commerce prompted a demand for large numbers of clerical workers: people who wore suits and ties to work, and lived in their own homes in the suburbs. These were not aristocrats moving down the scale; these were aspirational working-class folk, who wanted to separate themselves from their background.
Most of us are now pretty-much middle-class. Regional accents have softened; we're all familiar with middle-class manners and customs; farming and manufacturing nowadays employ very few workers. Most of us are more-or-less clerical workers now.
The "Bucket" behaviour is something I haven't observed for decades. Those "airs and graces" are indeed a middle-class phenomenon, not upper class. The real aristocracy eat beans-on-toast, swear like troopers, watch rubbish on TV, and are often quite uncouth. And they don't care what others think about their accent or manners.
What the author describes (the genealogies, the oneupmanship, the keeping up with the Buckets, the airs and graces) is upper middle class behaviour, aspiring to be part of the aristocracy.
The truth of the matter is that none of them ever had a hope - the aristocracy is a closed circle, and you don't even get in by marriage. Your children do, but you, no.
As a result of the incredibly close nature of the aristocratic circles in the UK, practically everybody knows everybody, and any outsider or imposter is usually very swiftly seen for what they are. That said, the close nature also fosters a relaxed social approach in general - you'll never meet people who F and blind as much as the old families. Feet up on the table after the hunt, crack out the cigars, pass the facking port, I'm dying here. You're constantly being judged - but not how you'd think. Nobody cares if you know your silver service (although it's a shibboleth, to be sure), nobody cares if you're well spoken or who you know, or where you schooled - all they typically care about is that you're not an arsehole, and that you're not going to try to nick the silverware or trade off their name.
Most of the time, in the UK, if you encounter an aristocrat, they'll look like they just clambered out of a hedgerow (because they probably did), and will be pleasant, amiable, and engaged in what you have to say - because they have absolutely nothing to lose by engaging with you, and you are possibly going to be an entertaining story over supper later.
I've hung out with enough aristo friends' families and enough friends' upper middle class families to know which I prefer - the middle class families are suffocating affairs with dinner gongs and rules around shoes and no swearing in the house. The aristos are... relaxed.
So. If anything, the upper middle classes are the dangerous cult, trying to impersonate the faded glory of a generally toothless propertied and titled class, and generally getting it utterly wrong. The aspirational class is the one that now stands on heads.
Also, virtually literally every aristo I know votes Lib Dem or Green. They've hated the tories since Thatcher, and countryside issues are of prime importance to most of them.