Have you tried the more aggressive approach to using the TPS as a weapon?

This consists of first asking where they got your number. Then asking what country they're based in. Then asking if they're aware that there's a legal requirement for them to check any number they wish to dial against the TPS list before dialling it. Then pointing out that you're on this list, and that they're phoning you illegally. Finally, request that you're taken off whatever system they used to call you, and point out that if you receive unsolicited telemarketing from them again, you will be writing to whichever governing body covers telephone sales (I forget, I think it's Ofcom).

This can be spiced up at the start by asking for their full business name, address and postcode after asking what country they're in. Also optionally asking them to repeat their name (Never ask for full name, they'll never give it. Most will start with a name, or give a first name if asked). This is done before mentioning the TPS to ensure maximum embarrassment when they suddenly realise that you're on the TPS, aware that they're doing something illegal, and they gave you their business address!

Oh, and the phrase "You're not legally allowed" (to phone me) seems to carry a lot more weight than "it's illegal", mainly because it contains more words for the meaning to really sink in from. Also, telling them that you "wish to ask them a few questions so you're sure you're talking to a proper company, working legally, and not someone who might scam them out of a lot of money" is a good way of making them think that you might be passingly interesting in whatever junk they're selling. The phrase "legally" in the middle is the catch, as you know that you can use that to hang them later in the conversation.

This particular series of questions, carefully asked in a somewhat interested tone of voice, I've picked up from my father, who once (apparently) made the poor girl on the other end of the phone gently sob after carefully trapping her with a series of questions, making her think he was writing down the answers and would be writing to both the company and Ofcom to complain about their lack of following of the TPS. He Never wrote anything. Successfully scared the girl.

So far I've found that the mere mention of the phrase "Telephone Preference Service" is enough to instill fear into whoever made the mistake of phoning up (with the exception of one person calling for market research rather than telesales - research apparently is not covered by the TPS). I remember one call where after a couple of questions (to begin with it could have been a legit call from the mobile telco) I casually mentioned that I was registered with the TPS. "Um... I'll just remove your number from the list then". I don't think I've ever had someone call me again after that.

Some research online shows the one that called me to be Kitchens Direct, apparently with a reputation for silent calls and ignoring requests to stop calling (the silent calls come from autodialers placing more calls than there are available people, and so dropping the extra ones if they connect). If they call again then I may well give your method a try - they've had me name the TPS once already, so they can consider themselves warned :)

And now there's a pop-up add at the top of your journal about freephone 0800 numbers........