We once were on our way to Devon in our MPV.
This guy/twat in his Subaru(with his company name plastered all over the side) kept undertaking, slowing down, speeding up etc etc while playing with a laptop.
We genuinely did not know were he had gone so we wanted to go in the services, indicated and pulled over, guess who was there?
He then followed us into the services, parked his car(no handbrake the car started rolling off down the carpark and he had to go back
) and made his way over to us, me and the wife are fairly well trained in Self Defence (10 years TKD/Mixed martial Arts/Bow staff etc etc) so stayed in the car while he rapped on the window asking 'you don't know who I am' to which I replied 'I do your company name is plastered all over your car'!
He made a sharp exit when he realised
.
I could have gone to the police but what would have happened? Some nutter finding out where I live? Ironically I owned a Subaru at the time!
Best thing to do is either, IMO, undertake at a safe opportunity i.e. when the hard shoulder is clear enough for emergencies, or just be patient and wait for an opening on the fast lane.
I never remonstrate anymore because there are some nutters out there who are willing to put everything on the line to prove a point, I have a few mates who are willing to do that too, its they way they are