You maniac!
I'd write back denying that you own or have ever owned that car.
Many many many moons ago I got an indignant letter from BT, accusing me of knocking down a telegraph pole in Oldham. At that time I'd never been to Oldham. They were quoting my registration, but the white transit van they described was actually a black Astra coupe. Furthermore, cctv at work clearly showed my car parked in the car park of a certain police station when the incident happened.
I wrote back to BT, but they would have none of it. I let it go to court, and produced exhibit a) VX02SEY, a black Astra coupe, as far removed as possible from a white transit, and b) a letter from my Supernintendo confirming that both me and VX02SEY were 150 miles away at the time.
The court censured the BT rep, and awarded me £300 compensation for my time and fuel. I also complained to the DVLA that they should not simply release owners details without checking the veracity of the request- had they done so they would have seen that my registration was not a white transit van, and would not have released my details. Alas, I got nowhere - all they care about is the income they make from such requests.