I think you can overide it via your online account for friends and known people as the number isnt witheld until in the BT system etc

The call will be flagged as withold CLI when it leaves the originating switch irrespective of operator.

As DaveI says Anonymous Call Rejection would probably work however that is a hefty chunk of money each month.

You mean 118 800, currently ammending the Beta

I haven't taken my number off. most people ring me during work hours. If its family/friends then i'll call them back later but otherwise I just leave it.

We dont get cold callers on our house phone, but my mate does (they are ex directory). I once answered and said I was Archangel looking for a way to get into contact with Airwolf

Yep, just lay the phone down and go back to it it 10 mins.

or put a 18month old onto them he loves talking on the phone (even tho he can't talk much yet, just hi ya's and a lot of babbling) . the guy was still talking away to him after a 30secs, the my son desided he was bored and said bye bye and put the phone down.. Priceless