Update: Having reported it, it turned out this van was registered to an abandoned pub in Peckham. Because of that the police couldn't trace the driver, and the 6 month statute limitation on common assault meant that the charge expired. I hope they caught him via ANPR at some point, the dirty scumbag.
So, my impressions? On the phone as I come past, I stop in the gap between him and the vehicle in front. He drives at me from behind, spits at me, goes through a red light, and then threatens to punch me.