As this Vectra passes Neil Hamilton's Rover (with him driving), if you look closely, you can see that cheeky kid in the back is holding up a newspaper with a headline about the Hamiltons scandal (which coincidentally happened just as Theroux was filming this documentary), hence why the filmmakers included this piece of footage.
The background cars on this page were added for a reason, the Corolla is being used by journalists and the Mercedes van is a TV van, otherwise I wouldn't have added such common cars.