I don't worry about what drivers might or might not do. I don't go left until I have somewhere to go, either an island defined by double yellow lines before the left turn lane starts or the turn lane itself. If there's traffic back, I simply come to a full stop, look back, and wait until there is no traffic back, then go over to the left turn lane or intersection, whatever it is. I very rarely have to stop. Usually I can adjust my speed so I'm in the right place when a large traffic gap opens. I use a helmet mirror.

I was once run into the right curb (US) while commuting to work over 50 years ago. It can be impossible to take the lane during rush hour BTW. But it was my fault. The car didn't touch me. I was ~4" closer to the curb than I should have been, so my being startled and too close to the curb caused the crash. I wasn't wearing a helmet and went headfirst into a phone pole, still in my toe clips. That probably explains a lot.