Please report dangerous drivers to the police - Roadsafe. Report to plod, not just whinge here.

It's easy to find out whether or not a vehicle is taxed and / or insured if you have the reg.

It's very difficult to find out the registered owner's (who may not be the driver) address from these details. You need to have a valid reason why you want their address, for example they've parked in front of your garage blocking it and you believe the vehicle has been abandoned - you'd also have to provide photographic evidence.

I've done this. I wrote to the DVLA and said the vehicle was blocking my driver, I think I paid £4 and they sent me the registered keeper's details.