The DVLA keep mis-sending letters to my house?

A few months ago, I received a letter from the DVLA address to a Mr Daniel Fitch; no one of that name lives or has ever lived at my house. The letter had my address and town, but not my postcode. Then, they just wouldn't stop coming: there were weeks when I was getting three or four letters for Mr Daniel Fitch.

Numerous calls and letters to the DVLA later, I finally managed to persuade them that, no matter what their computer said, Mr Daniel Fitch doesn't not and has never lived at my address. They said they would change their database to reflect this while review the case. I had nothing to fear from this and, when a few months passed and I received nothing from the DVLA for Mr Daniel Fitch, I assumed they had also concluded he didn't live at my address.

Well, you know what they say about assuming... I received another letter today from the DVLA, for a Mr Daniel Fitch. I don't know what else to do now; I've spent hours on the phone telling them everything I can, then writing the same things. They've changed their database and presumably conducted their own investigation, and *still* the letters comes. In addition, I've gone up and down my road, asking for Daniel Fitch, and no one seems to have heard of him.

What else is there to be done?