There was an official design of road in England when I was a child: three painted lanes. The middle lane could be used for overtaking by traffic going in either direction. I hated when my dad would overtake using this lane. I could see from the way he was concentrating and pushing the car to its limit that it wasn't a comfortable manoeuvre, and it generally seemed rather pointless as we'd soon be stuck behind a line of vehicles that was too long to overtake.

It looks like they've all been removed, even the tiny bits this page says still exist:

https://www.sabre-roads.org.uk/wiki/index.php?title=S3

That practice fortunately fell out of fashion with the advent of proper infrastructure - instances of this are now rare because other drivers usually don't know what's going on, so they don't move to their right.

Two or more cars overtaking at the same time is still a thing though.

That being said it's still part of local "car body language" that you move to the right if you want someone to pass you. Using your right indicator in turn says "I am going to make a sharp turn to the right now", so you'll have people behind you hitting their breaks if you do it. I occasionally use that to stop people from tailgating me.

That is mandatory to do outside of the city afaik. Many people keep having in the city too consequently.