The problem with most nuisance calls we get is that they continually change the caller ID which means you have to have at least one before you can block that number. I am registered with TPS and on the only occasion I can remember where it was a real company calling I mentioned this and immediately got an apology and confirmation my number would be removed. All the others we get are either because of the TT fiasco which actually have reduced in number now to maybe a couple per month, and a new one being supposedly an Accident Insurance claim company with Indian callers again, two of those in the past couple of weeks. Again different numbers each time. We are ex-directory, and have been for some 20+ years and that I believe has had an effect on reducing the amount of nuisance calls we get, as at least companies who use lists wont find us easily, we also have anonymous call reject set on our line, only issue there is our son cannot phone from work on his work phone but since he knows that it is not an issue, however the Indians still get through because they are spoofing caller ID and it confuses the rejection software.
Most spam/nuisance calls these days use number generation and caller ID spoofing and again are outside of the UK and EU so nothing much can be done until their own jurisdiction does something about it.
Stuart