Vegas himself has not commented fully but has said
I haven't done anything wrong(ETA: since I wrote this, the Press Gazette has covered the story and has comments from Vegas). Given the nature of the UK libel laws this makes sense—his lawyers will've told him to stay quiet and not mention specifics, and they'll likely push for an out of court settlement. If it does go to court, unfortunately, the odds are in his favour to win the case. English libel law notoriously favours the plaintiff and all he he needs to demonstrate is that his reputation was hurt (uncontestable); the Guardian'll need to, they need to demonstrate that their version of events is a reasonable interpretation (and he'll only need a few audience witnesses to say otherwise unfortunately). Teh Graun pretty much needs the girl herself to come forward else they've lost. Have I mentioned English libel law is an arse? I think I might've.
Of course, he does have a few witnesses on his side already, this commenter at the Evening Standard Comedy Blog for example:
I too was at the show on Friday and from my vantage point in the second row, I can honestly say that the female audience member in question appeared to thoroughly enjoy the experience. Coming off stage she looked as if she had just won the lottery.and as Chortle observes:
Did his ‘victim’ feel uncomfortable, too? Undoubtedly. I certainly did. Did she feel abused? Only she can tell. It’s the million dollar question that Vegas’s reputation rests upon. Or maybe the damage has already been done.We'll be watching this one closely I suspect. Tim? I'll be in touch mate.
 Guardian has removed the story as a result of the action, it was here.
 A few of the articles I link to have now been removed or locked down by the sites that published them due to liability concerns—no one wants to get sued for libel. Worth reiterating to commenters that under the T&Cs of Livejournal, each individual is responsible for their own comments—this is a public post and Schillings have a rep for searching blogs (see tag).
 From Tim at Bloggerheads in his post linking here. ( A note for non-LJ commenters )