Actually the Brits aren't being original here. The term 'Liberal Elite' has been in use in the United States for many years, at least since the Vietnam War era, and the idea goes much farther back then that. The phrase was employed to a large extent by conservatives in the 80s as they tried to promulgate their fiction of an odious and high living conspiracy of effete academics and welfare queens who are out to bilk the common man.
To a great extent the 'liberal elite' still have a place in the public consciousness, especially among loser day-traders who sit around and watch stuff like the O'Reilly Factor. The image in the U.S. is of a well off and well educated person with liberal politics who disdains common values from on high. This person, despite their book smarts, is in reality rather lazy. Their liberal politics are seen as hypocritical because they personally have some money. Often the image invoked is tinged with an undercurrent of antisemitism. They are assumed to be involved in some combination of academia, Hollywood, or the media, and therefore wield influence over society.
Anyone who is actually a liberal or on the left in the U.S. knows that this is entirely laughable. Hollywood and the media might as well just drop all illusions and go give sloppy head to the Heritage Foundation. Some academics have some money, and a few of these are leftists, but most work long hours for low pay. It also seems to be common to confuse living differently with living wealthily. Some leftists are barely getting by, some have middle class lives, and a small few are what we would consider rich. What of it?
There IS a sizable segment of American society that is urban, successful, centrist in their economic politics, and vaguely tolerant in their social politics, and these people do indeed constitute a powerful elite, but they are not liberals or on the left. However, some of their outward trappings seem to be those of liberals, and therefore their existence lends some confused credence to the belief in a liberal elite among more downtrodden elements of society.
The ultimate irony, of course, is that as the 'common man' focuses his anger on this fictitious entity, the true elites of society continue to screw him. Ha ha, joke's on all of us!