As I pointed out, this has nothing to do with 'national security'.
Here you can ring up the national population centre and ask for anybody's address. When I worked in insolvency practice we had no problem in finding people and discovering what assets they owned via Land Registry and it was all quite legal.
Nobody cares. Why do you keep mentioning it when it's totally ******* irrelevant?
You cannot determine an owner's name and address via a car reg. IN THE UK except by written application to DVLA, and they will want a good, well-documented reason and are notoriously slow.