I've had one spate of calls a few weeks ago of the "silent, number withheld" type, and a few with strange and unlikely numbers. Eventually one spoke and got told where to shove it, and its one place where the sun rarely shines. Then the calls gave up.
Got another today. Nearly pronounced my name right, had a strong sub-continent accent, and called himself "Mike", sounded more like a "Geet". He claimed to be from a software support company, then promptly cut himself off.
1471-ing him, I got 034009054. A google for that turned up a few "complaint and muttering" sites, so it seems that "Mike" is a scammer. He would, if he manages to avoid cutting himself off, like you to download some software to let him and his mates loose inside your computer to enjoy the fruits of your internet banking passwords.
It would be nice if there was a central reporting point for these scammers, so that they could be officially found and trodden on early, but as I suspect that most of them are out of the country, it might be difficult to implement.
So, if anybody rings out of the blue, asking you to do things with your PC, just let them talk. It will increase their phone bill, and my pension fund will be happier. If they pay their phone bills.