Re the OP, it's a question I often ask myself. Often just after I have given a little wave to someone who has stopped, as is my habit. Of course only people who looked like they were stopping anyway get a wave. If I've had to force the issue by stepping out meaningfully - they get treated to a slow walk and get ignored. These rules are so complicated, who invented them? Oh, I did.
Re other drivers giving way to other drivers at junctions etc in heavy traffic. In my neck of the woods (Sarf East London) people will nearly always let you in, but you do have to be clear about your intentions. If it didn't work like that, everything would grind to a halt. The South Circular is a tremendously effective traffic-calming device.