Spotted...

wx54 cxf (i think) was his plate.
anyone know how to trace this?

I just entered his registration into http://www.askmid.com/ownvehicle/

WX54CXF is NOT on the Motor Insurance Database today

By allowing someone to drive this vehicle, the driver is at risk of being STOPPED by the police and having their vehicle impounded, and possibly DISPOSED OF, if proof of insurance cannot be provided.

That might explain why he didn't stop - and will almost certainly make the police more interested in the case. Did you call them? If not I'd head down to your local station asap. Were there any company names on the lorry?

Edit: could also mean the plate number was wrong though.