Some people may know about this service already, but if you havent it can be very useful to have a look. Stop cold calling etc with this service by registering with them. It's free to do and allthough i've had a few companies slip through their net on the whole i get very little cold callers compared to before.
The Telephone Preference Service (TPS) is the central opt out register on which you can record your preference not to receive unsolicited sales and marketing telephone calls to your home or mobile telephone numbers. It is a legal requirement that all organisations (including charities, voluntary organisations and political parties) do not make such calls to numbers registered on the TPS unless they have your consent to do so.
h**p://www.tpsonline.org.uk/tps/
(replace the ** with tt)