I'm not sure that listening to UK ATC in non-real time
is legal. Do you have any reference to something official?
Heathrow is still explicitly warning
plane spotters:It is illegal to listen in on ATC communications between ATC and pilots if you’re not required to be listening (for instance, if you’re flying in the same region). You can listen to ATC if given permission, e.g. at an air show.
I think the legal issue still comes from the "Wireless Telegraphy Act", a law that has roots back to about a hundred years ago, when all sorts of private communication/telegraphy was transmitted using unencrypted signals. The law restricts people to listening to public broadcasts only - while intercepting any private/directed communication was made illegal, unless you had explicit authorization.
In theory, it's also illegal for pilots/controllers to listen to ATC transmissions when they are off duty. There's a similar issue with other, mostly European countries. In practice, I don't think this law is really enforced for ATC transmissions - officials turn a blind eye, unless the interception is too obvious. A policeman once told me to better turn the volume down or use headphones...
. But I suspect that streaming transmissions via liveATC would be a little too obvious - and authorities would eventually object...