@Thogg can't help, even if he wanted to. Data protection laws restrict trawling of such data. He would need to work for that area and be assigned the case to make enquiries. (just been through this with our local PCSO after Loz Jr had his bike reversed into and damaged at work)
Anyone can use the DVLA site to query a plate these days, but if its not valid its not valid.. If it comes back as valid and it looks like a match you can fill out the data request with the dvla and if they deem the request valid they will send you the owner. But as we have all surmised, its a false plate.
As long as its reported and a marker put on that plate it will ping up on APNR if he is stupid enough to keep using it.
Check if a vehicle is taxed and has an MOT is the gov site for this and recently was deregulated to make it open. (previously you can to say that you were the owner etc.)