I'm more concerned about a non-law enforcement agency having access to the registered address of the car owner.
I was out and about in the car a few weeks ago and the McD's Gatwick situation was discussed at length.
It was quite a well researched piece, with legal input. Bottom line IIRC is you can get vehicle registered keeper data if you have "reasonable cause". There seems to have been some legal activity in the recent past, where the reasonable cause has been interpreted to mean parking enforcement by civil organisations is acceptable. Sounded pretty odd to me.
A quick look on the Information Commissioners site (who had someone on the radio segment) would indicate they are looking into this.
Link here but it's a 10 page pdf, if you are that interested..!