It is actually illegal to listen to anything to which you are not licenced or have the permission of the user to do so
(Wireless Telegraphy Act 1949.) It is also a popular misconception to think you can listen to anything so long as you don't pass it on. Have a look at the Radiocommunications Agency site
http://www.radio.gov.uk/ and search for information sheet RA169.
From a practical point of view, so much air band listening goes on I don't think anyone is going to get very excited about it, particularly if it is for an eminently sensible purpose of improving your own RT standards. But you did ask!
