sorry mach 78,
It is ILLEGAL in the UK to listen to the police.
From RA169:
Although it is not illegal to sell, buy or own a scanning or other receiver in the UK, it must only be used to listen to transmissions meant for GENERAL RECEPTION. The services that you can listen to include Amateur and Citizens' Band transmissions, licensed broadcast radio and weather and navigation broadcasts.
It is an offence to listen to any other radio services unless you are authorised by a designated person to do so.
There are two offences under law:
Under Section 5(1)(b) of the WT Act 1949 it is an offence if a person "otherwise than under the authority of a designated person,
either:
(i) uses any wireless telegraphy apparatus with intent to obtain information as to the contents, sender or addressee of any message whether sent by means of wireless telegraphy or not, of which neither the person using the apparatus nor a person on whose behalf he is acting is an intended recipient;
This means that it is illegal to listen to anything other than general reception transmissions unless you are either a licensed user of the frequencies in question or have been specifically authorised to do so by a designated person. A designated person means:
the Secretary of State;
the Commissioners of Customs and Excise; or
any other person designated for the purpose by regulations made by the Secretary of State.