I used to work for the police and they use a VODS (vehicle online description search) search faciltiy on PNC - this is a really powerful tool which can be used for searching partial vrm with details of the vehicle.
I remember being told whilst been trained that one of our forces officers had been watching Crime Watch which featured a case where they were searching for a gang that robbed a bank not long after the introduction of this search facility. He got back to work and had a bash at trying to work out the vrm and got a hit using VODS - called the force in question and it turned out they had not tried it yet - red faces all round when they realised he had the right van!!