The big case here is that UAL isn't broadcasting that or 'rebroadcasting' that out to the public masses, and is staying within their aircraft. For all intents and purposes, Ch. 9 is like closed circuit TV; only going to the people who can hear it (which is only in that aircraft). If it were being retransmitted across a far wider medium, such as the internet or radio frequency, that would be another story.
Looking deeper into Ch. 9, all that it is is part of the IFE, which has nothing to do with retransmitting or broadcasting. As it's a feature of their IFE service, it doesn't cross the line according to UK law.
Please take this as my opinion; IANAL.