Registration # information is public in the UK. You can just scan any vehicle on the road. I don't think ownership info is, but you can get all the detail of the car it belongs to (or is SUPPOSED to belong to).
Ah, this makes sense (not necessarily that this is public information, but why the scanning works)
They almost certainly don't, most likely there's some lookup table to find VIN from a license plate. I live in the US but I just looked up my VIN correctly by my license plate on VINcheck.info