woman11017, what would you be reporting him for, exactly? Wearing a dress? I reckon most feminists would say it's OK for men to wear dresses, and that people shouldn't be fired for not conforming to sex-roles around dress and presentation.
Or did you mean the 'banter' with female colleagues? This is fairly vague, as banter could cover anything from, well, banter, to sexual harassment.
Sorry if this sounds overly interrogative, it's just that your post set off some warning bells for me, in the sense that maybe it's intended to goad some Mumsnetters into saying that men should be reported to their employers for presenting in feminine dress, and presenting it as 'evidence' that we want trans people fired.
If there's more to the story then feel free to elaborate in another thread (as this one pertains to something else).