This deserves a wider audience.
OK, I understand that the criminal justice system is a bit busy at the moment, but let's try and find time to prosecute these drivers. His point about ambulances is spot on, but it's not the only reason.
The same thing happened next to me once, and when I did finally get to a junction that I could use, I couldn't get off the motorway because of all the people pushing past along the hard shoulder on my inside. Eventually, just I had to put on the horn and the indicator at the same time and go for it.