No urban myth about Max Miller, though he was not banned immediately by Aunty Beeb. I remember he used to ride the edge, until he couldn't resist any longer, and he would suddenly go off air, followed by an anouncer apologising for the technical hitch which is "beyond our control". Then, after a short silence, "We are now returning to the (whatever show it might be), and Max would be heard no more, that night.
They may have banned him later, because he did disappear from radio, or maybe he just got fed up being cut off. BTW, he did say in an interview, that he was proud never to have told a dirty joke in his life, he merely made comments and left it to the dirty minds of the audience to make the connection.