Surely overtakes are meant to be on the right? If a car was turning left in front while I was driving, or moving at a reasonable speed, I wouldn't cut through on the inside even if for some reason there was space, why should it be any different on a bike? In both cases the vehicle in front, turning, has priority.
I had a shock the other day, had passed a lone cyclist then came up behind a small group and stayed behind at about 20mph as not safe to overtake, even if it had been they were stuck behind a farm vehicle so would have got me nowhere. Not a particularly wide country road, with some tight spots at bends. I'm always checking my mirrors, very fortunately in this case as I suddenly realised that the lone cyclist had pushed his way into the gap between me and the hedge, couldn't get in front of me as I was behind the group, so he was riding in a space that could have been reduced to virtually nothing if a wide vehicle had come the other way. Seems he thought having half a car length between him and the others instead of a full length was worth the risk of being knocked into the hedge, which seems a rather dangerous attitude considering the number of drivers who don't use their mirror to check that area of the road unless turning (or at all), as they just wouldn't expect anything to be there, especially at that type of speed.
I have had so many idiots nearly knock me off my bike, my former housemate has been knocked off by drivers not looking where they're going, but the situations described in this thread can only exacerbate the anti-cyclist view sadly held by many motorists. Whether on bike or in car, surely people should use good old common sense to decide what is safe and what isn't? It's my opinion that anyone taking their driving test should be made to ride a bike through city traffic as part of it, just to teach them awareness... but sadly there are idiots on both sides, equally indefensible.