I got one of these a couple of weeks ago and wrote back to them, asking where they got my name from and asking them to delete it from their database. I didn't sign the opt-out form as it was to request that my name be "suppressed" from their database, whatever that means. They wrote back saying they got my name from the electoral register some years ago (before it was made illegal to do this), and confirming my name was now suppressed from their database. I still don't know what that means, but I gave up at that point. As far as I know if you don't opt-out, you're leaving yourself open to receiving junk mail addressed to you. See [broken link removed] for more details on this.