It's very very difficult to judge scale and distance in these films (more so as most of us aren't used to the 'bent-eyed view)!
So I think 2 things are important:
- was the bus actually scarily close TO YOU? (I don't care how close he was to the car!)
- your road position: it looks like you forced the bus into moving way over the white line to get past.
Taking an "assertive" road position, for me, is mainly about stopping vehicles squeezing past. If they decide to overtake putting OTHER vehicles (or their own) at risk, that's their problem - you've done all you can.