YANBU, but it doesn't help that motorways aren't covered in driving lessons. Therefore it's not surprising that people don't know how to drive on them.
One thing I've never been clear on is that if you have a scenario where you are already in the inside lane, doing 65mph say, and ahead of you are two queues of traffic in the middle and outside lanes doing 60mph - is it undertaking if you carry on making progress in the inside lane? Should you:
a) carry on and only move over into the middle lane when you need to overtake another vehicle in the inside lane, meaning you are passing on the left of the vehicles in the middle lane,
b) slow your speed and hang back from the traffic queues to avoid passing on the left, whilst remaining in the inside lane, or
c) join the traffic queues to avoid passing on the left
A) looks like undertaking, B) seems completely illogical and C) only exacerbates the problem of the traffic queues.
This was a situation I often experienced on the M27 and I was never sure of the correct action.
Would undertaking only be moving from the middle/outside lane inwards and back out again, specifically to undertake a vehicle, or does it also count if you're just in the inside lane anyway and it's empty because everyone else on the road is sat in the middle lane?