Liz, Debrett's can't be that good a yardstick for class - they stooped low enough to have me it for a while (by virtue of marriage, I'll admit)!
Unfortunately there will always be a class system in England - it seems to be hard-wired into the Anglo-Saxon psyche, and the more money that the great mass of the pople have (thus eroding the economic distinctions) the more that the behavoural and cultural distinctions will come into play as people adopt or even invent shibboleths to show that they are in some way superior to someone else. Just pick up a copy of the Daily Mail or the Express and you'll see a host of articles designed to reinforce the worst kind of societal distinction.
Even if we were to become an idealised socialist state, you'd still find a nomenklatura and a pool of people desperate to ascend to that status. It's one of those depressingly English things - as if the trainspotter's urge to pigeonhole and collate everything has been applied to people, underpinned with a large slice of insecurity and prejudice.
The worst offenders always seem to be the middle classes, who constantly seem to be in need both of scapegoats and aspirational models; thus spending their lives in a constant twitch of anxiety looking over one should and another to see wherre they stand in the pecking order.
The true working class and the upper class have far more in common, including a disdain for class distinctions, liberal use of the workd 'fuck' and an ability to enjoy themselves whatever the neighbours might think. Just visit any racecourse or beaters' day on a shoot and you'll see happy co-existence and proof that the 'old order' chugs on.
Bizarrely, though, there's a trend now among the upper classes to speak Estuarine English, together with lashings of glottal stops and rising terminals. All of when means that anyone you hear speaking RP is either over 40, a counter-jumper or - horrors - an immigrant!