Register at Telephone Preference service and you wil get less cold calls. Free service and can register online.
Similar service for snail mail at http://www.mpsonline.org.uk/mpsr/
What is TPS?
The Telephone Preference Service (TPS) is a central opt out register whereby individuals can register their wish not to receive unsolicited sales and marketing telephone calls. It is a legal requirement that companies do not make such calls to numbers registered on the TPS.
The original legislation was introduced in May 1999. It has subsequently been updated and now the relevant legislation is the Privacy and Electronic (EC Directive) Regulations 2003.