What's stuck out to me and, subsequently led me to this post, are the accents of King George VI and Viscount Halifax. They both seem to pronounce 'R' sounds with an almost-German accent (especially Halifax). In real life, they're Ben Mendelsohn and Stephen Dillane, respectively, and are Australian and British. Their characters are British. But, I can't help but notice the glaring, back-of-the-throat R-sounds coming from both of them throughout the movie.

Sorry, I know you're more specifically talking about Churchill's accent...to me, he sounds nearly exactly like he does from his real-life radio broadcasts, though.

Still, you did refer to the King, so you and I can't be the only ones noticing the dialect (I suspect you and I might be talking about the same, or similar, thing that we hear when he speaks). It does indeed sound like a 'W' when he pronounces a word like, well, 'pronounce', and I hear a 'R' in the back of his throat, like a German. Probably the same thing, right?

It bothered me enough that I just had to see what actor played Halifax, thinking he might actually be German, but then I realized it's just good ol' Stannis the Mannis (Stannis Baratheon from Game of Thrones). No German there.

Maybe my American ears are hearing things wrong or, more likely, the accents are deliberate and were researched heavily by both actors before they utilized them in the film...However, this is the first time I've heard HRM George VI with such an accent. The actor that played him in The Crown has an entirely different accent: more clipped/aristocratic/royal, with absolutely no strange 'R' sound(s).

Guess we're stuck to ponder this ourselves?