I would like to see PlusNet customers lobbying PlusNet to look into offering some kind of call filtering; namely: caller authentication; or VoIP SEAL?
http://www.voipnow.org/20...7/04/10_tips_to_filt.html

Frankly, I don't get or want a lot of calls on my landline, and I know whom I give it to.

Much as I'd rather have letters with a barcode dictating whether they go in my letterbox; I'd like to be able to set a list of accepted numbers; or possibly give out an access code to people.

I'm sick to death of jumping out of the shower to grab the phone thinking it's an emergency just to hear some idiot ask me if I want double glazing.

You could try signing up to http://www.mpsonline.org.uk/tps/. 

Since signing up we don't get cold calls for double glazing, insurance or having new patios installed.

Great link TheLaughingBuddha.

I signed up about 1 1/2 years ago and i now i only get an odd call though mainly from companies i have things with IE my bank asking if a want a new credit card.