The Highway Code clearly states that you should not allow other drivers affect the way you drive (I.e. According to the rules) but it's clear with the Peugeot at the start of the clip.you ease off the gas to hold him up when he tailgate you. Then you put your foot down when he changes lane. You then put your foot down again when he overtakes the estate car. At this point you yourself are speeding in the 50 Zone. Your intention was clearly to try to block his way back in to your lane. You failed. He drove like a nob. You drive like a mob and was probably lane hogging to boot.
Speaking personally. Seeing as the BM was just at the width restriction before you, I would have just let it go rather than make some sort of point.
On this point, a few years ago as reported in my local newspaper, the council put in one of these width restrictions. Later the local constabulary informed the council that it was a dangerous obstruction with the potential to force vehicles into a head on crash situation. It was very quickly removed.
I hope that clip has been given to the police for failing to stop after an accident investigation