It's one thing reporting (anonymously) to the police if you're worried that someone may have been hurt. It's a completely different thing to record the conversation and give the recording to a national newspaper.
Why? The conversation was loud enough to be heard in a neighboring flat. This is by definition a very public conversation, almost a public speech really.
Installing a hidden microphone would be different, recording a conversation that doesn't require more than a smartphone app in your own home isn't that controversial.
Note the story is now that they only contacted the newspaper after the police had already informed them that no one had been harmed. Simply a smear campaign by anti-tory and anti-brexit newspapers aided and abetted by hateful neighbours.
I'm not sure a "smear campaign" applies here, "dose or reality" seems much more appropriate.
McHrozni