The new cameras they have now a very sophisiticated and its possible the one you saw was also a number plate recognition system aswell (the police are very big on them at the moment) so the officer could very well have been looking at a monitor in the back of the van.
Can you remember if it was just a regular transit or a larger type van? Either way you might have got away with it because the big van is looking for tax dodgers/ uninsured drivers/ stolen cars etc and the small one would need an operator. i think?!?