Thanks to the magic of VoIP (worth a string of blog posts in its own right), I haven't had a real landline phone in years. But many traditionalists, notably my parents, still do. And when you've had the same number for 30 years, despite being registered with the TPS, you tend to get a lot of junk calls. Often, these come from abroad.
TalkTalk deserve mention for being better than BT in that they don't have the cheek to charge for caller ID (though you do have to dig into their website to turn it on). But still, scrambling to reach a handset and see "unknown" flash up on the display so you can reject the call is tedious. And it only works for extensions which are modern enough to have a display.
All this did lead to an excellent Christmas present idea for my parents, though - devices called call blockers exist which can automate rejection/filtering of calls from unknown numbers.
My first attempt was the CPR All-in-One Call Blocker. My advice would be "don't bother" - the unit I got was dead on arrival, and its use of non-BT sockets made it hard to daisy-chain my parents' wired extensions off the output side of it. It's a flimsy black box which inspires no confidence.
So I upped the ante and ordered them a TrueCall. This has proved much more like it - easy enough for my mother to install; uses standard BT sockets on both the input and output sides; Just Works. It's blocking an average of two calls a day, and my parents are delighted with it. And, despite mixed reports on the internet, connecting the extension wiring to the output socket allowed my parents' two wired extensions and cordless phone to all take advantage. As the icing on the cake, mum was happy to program it using the touch-tone interface rather than the website, which means that she won't need to cough up a subscription after year 1.
It's also worth noting that the TrueCall is a much more complete solution - rather than blocking withheld callers and a blacklist of numbers, it can be set up to reject anonymous/foreign calls, it has both white and blacklists and it can challenge callers to identify themselves - it rings the phone, plays their name, and the recipient can then decide whether to pick up or bin the call.
Update - so I've now visited my parents and seen the unit for myself. Three months in, they're absolutely delighted with it, and a peek at the logs show that it's rejected a large number of withheld and foreign calls. It takes over answer-phone functionality, so again, a trip to TalkTalk's website to disable their default voicemail was required.