If there is no room to join just slow down, even stop, why would you continue driving into a ditch? O_oYou need evidence (dash cam recording)
Some years ago (before dash cams) I was just getting onto the M1 and indicating as normal and a van picked me at random to block me getting onto the motorway. He sped up and then slowed down and basically blocked me getting onto the motorway and forced me into the ditch off the hard shoulder. I stopped and called the police and they were not interested at all, gave them the van reg and everthing.
Without video evidence and an independent witness you have nothing