The recording and monitoring of telephone calls is governed by a number of different pieces of UK legislation, which includes;
Regulation of Investigatory Powers Act 2000,
Telecommunications (Lawful Business Practice)(Interception of Communications) Regulations 2000,
Data Protection Act 1998,
Telecommunications (Data Protection and Privacy) Regulations 1999,
Human Rights Act 1998.
The limited set of circumstances in which a business may record or monitor your call (which they need not inform you they are doing) is listed here...
http://www.veritape.com/LegalityUK.html
It is also not illegal for individuals to tape conversations providing the recording is for their own use, under the Regulation of Investigatory Powers Act 2000 (RIPA).
It is a civil, not criminal, matter if a conversation or e-mail has been recorded and shared unlawfully. If a person intends to make the conversation available to a third party, they must first obtain the consent of the person being recorded.