Where It All Goes Down
A not-so-distant future city or town in England.
Considering that the novel was written in the 1960s, we're probably well past the dystopian futuristic setting Burgess envisioned for this work. Come to think of it, though, what constitutes the "heighth of fashion" in this work is still a bit more futuristic (read: bizarre) than what we've seen in our time, so maybe give another tack on another twenty years to imagine when that "future" ought to occur. It is worth noting how the macabre and filthy streets add to the "sensation" of this being a gross, dystopian city in the future, though.