For a fee, and with sufficient proof of 'reasonable cause', DVLA will supply name and address of registered keeper. This is how a parking fine ends up landing on your door mat...
You just write to them and say it's for legal purposes and they'll give it to you. I used to do this years ago before it became common knowledge. You don't even have to issue any proceedings either because they never asked for any proof. Bit of a loophole in the system.
