It's for landlines thats all I know. 
I have a app called blacklist on my jailbroken iphone, 
I can add from address book or recent calls. 
plus all 0800/with held and private. 
Plus as previously it's always a good idea to register all your lines no matter what they are with http://www.tpsonline.org.uk/tps/index.html 
  
It's is free and puts your numbers on a list of not to be called. 
Although this alone does not guarantee that people will not call you it certainly filters out a good 50% of plonker calls. 
And it is against the law to cold call numbers on the list. 
I suggest you do some research for anything else with cold call as they may have something for Mobiles. 
I have call blocker on a virgin landline.