ok I've said this before, but here goes again- I used to ride to work every day for years - be it to Ashford beyond Heathrow, Apsley out beyond Watford or Clerkenwell, all from Harrow, and I have the scars to prove it, broken leg, chipped teeth, broken and surgically mended shoulder.
In my time I've many an altercation with busses (as well as cars but I want to concentrate on the buses here) and do know exactly what peeps suffer.
Yes by all means stop and say what you think without losing the temper ideally, and I DO know at times I could have killed.... however, the neat trick is to write down/photograph the offending vehicle, its reg no, its bus route no., the time, any witnesses, and finally the bus company name.
Next is to write to the bus Co with what ever evidence you have explaining in simple terms what's been done that's wrong. The bus and driver can be traced very easily. I found every bus Co took the trouble to respond to me, and advise their actions, and they were pretty stern about them, they'd taken with the driver ie their card is marked- both bus Co and driver.
The driver holds a Public License and if he/she loses that then its no earnings, card marked for being sacked, and more difficult to get another job- simples.
I've had similar success with liveried lorries/vans on the roads and motorways too (I don't make a habit of it!) and have found it very effective- although at the time it was a phone call to the Co concerned about thier idiot driver. Driving at the same time as phoning is now a no-no.
IIMHO the taking of details and the writing is well worth the effort.
I'd just love to have been a fly on the wall when the case was mentioned to the drivers concerned.
Shortage of bus drivers means that not an issue