This came from Ofcom today
'Illegal broadcasting is a menace which can cause interference to safety of life communications services and legal radio stations,denying listeners their choice of service. Ofcom, together with the police and local authorities takes swift action against this illegal activity. Ofcom today published a factsheet on its work in tackling illegal broadcasting, which contains information on how to contact
Ofcom to report illegal broadcasters.'
The factsheet can be found http://www.ofcom.org.uk/radiocomms/ifi/enforcement/illegalbroadcast/factsheet.pdf