SPB said: "I would kind of like to know how two different police forces got my address when the licencing authority have stated categorically that the vehicle is not registered at my address so there is an on going data protection issue which I would like to have resolved too as there is a duty of care which owners of databases should be adhering to."

This may not be relevant in the UK but for a time it was possible in our state for unethical self serving low-lifes to submit a statutory declaration advising that another person at a different address was responsible for speed camera and parking offenses etc. (This only worked on camera and parking offenses etc because otherwise the police officer dealt with the offender in person.) They got away with this trick for a while until the powers-that-be decided to change the rules. Another trick was to go to the motor registry and submit a change of address on the vehicle registration or driver's licence account. That is what I suspect has happened to you.

Usually the state government department would deal properly with the issue when the targeted victim notified them.

When all else fails it's a good strategy to contact your MP and provide the details of what has happened, what actions you have taken, copies of relevant documents, and a request for action to be taken on your behalf. The MP can diplomatically lean on the relevant department/s. The only advice I would give on that strategy is not to go to the MP until you have tried other avenues and had no success. You appear to be at that stage now because this has continued to occur for over six years and, as you suggest, this person is repeatedly getting away with unlawful behaviour.