I've registered all of my numbers with the TPS. I actually got a marketing call once and I told them I was on the TPS and to remove me from their lists. Then about a week or two later somebody else called me from the same company trying to get me to buy double glazing. I complained to the TPS and apparently the company was then fined several thousand because they'd had complaints from others as well.

It does work and you do it to mobile numbers as well. Before I used to get random companies phoning me up to try and make me take out a new contract, haven't had one of those in years now.