Totally agree with comments by TD and AA above however this situation is slightly different.
It isn't the radio station that is refusing to allow idiotic and dangerous conspiracy theories to be be aired, it's the regulator OFCOM who are threatening to sanction the station for permitting the woman to spread lies on their station.
It does raise an interesting example of the limits of free speech.
I think you could argue there is a direct and immediate danger of physical harm to others which is perhaps the only legitimate reason to disallow speech.