As part of my commute is down a narrow A road, I've been observing a lot of passing behaviour from cars.
(1) There are a substantial number of drivers who will, when there's nothing coming the other way, pull right out and make a huge, gracious overtake. Pretty much all professional lorry drivers will do this.
(2) There's a number of drivers who even faced with an empty oncoming lane will not give an inch when passing. I'm no gutter monkey. Even if I'm in primary, I think they'd arrange to pass with a centimetre-thin gap. After six months, I can safely say that every Audi driver falls into this category.
(3) There's the ones who will always squeeze by regardless of space or oncoming traffic.
(4) There's a teeny, tiny minority who if there's no space behind will wait until there is. Professional lorry drivers mostly, the 4x4 drivers who realise they just won't, and the few remaining drivers who have remembered courtesy.
Overall, I'd say that overtaking is consistently piss-poor. There's rarely enough space and zero tolerance if I do fall off or weave. The close pass is probably the most off-putting thing about cycling on British roads. I'm genuinely thinking of putting a big sign on the back of my bike (one that's about two metres wide) asking drivers to give me space (I may be making a mistake to think that Audi drivers can read). The annoying thing is that a nice, wide pass would rarely precipitate a delay of more than a few seconds to their undoubtedly very important days.