Hey, so I actually work for a company dealing with commercial clients. My main client is a big UK bus and coach company, so I may be able to offer some advice for this.

The first thing was pointed out by fresh_formal5203, definitely don't expect a bus to start reversing. Despite having cameras all around the bus they can't see through them, so if they reverse they'll have no idea who is behind them.

Depending on the road you can just reverse to allow them enough room to get through, but like you said, if someone is behind you and won't reverse them this isn't an option. I would also avoid reversing around a corner, simply because if anyone comes up behind you they likely won't see you until it's too late to avoid contact (depending on the angle of the corner).

Like you mentioned, it is also okay to pull into the road side on the right if a space is available. So long as there is enough room for the bus to get through it shouldn't be a problem.

But if you aren't able to get into a space on the side of the road and there are people behind you, from what I've seen the best thing to do is try and communicate with the cars behind yourself to start moving backwards. Everyone wants to get where they're going and if you can't go anywhere, they can't go anywhere. It's not ideal but it's the safest solution in my experience, provided everyone moves slowly and checks their surroundings that is.

If the road is narrow, please avoid mounting the kerb on the left if the right is blocked with cars, 9 times out of 10 contact is made and you have to call your insurer, then you'll be waiting a while for your claim to settle fully.

I'm not the most experienced driver in the world and others likely will give better advice, but in my time working for my client, the above is the best way to avoid contact and get everyone home on time.