I may be behind the curve here, but I've just discovered that the webwise site is now serving UID cookies to Virgin Media customers via a.webwise.net. The content ("unique" identifier) in the cookie seems to fit the stated format for a production-version Phorm cookie.
It occurs to me that even if, as they claim, VM have not trialled the Phorm DPI kit in their customer network yet, if they ever do, then those of us who are curious about the technology and have visited
www.webwise.com to find out further information will immediately be identified to the interception kit by this cookie.
This could result in the mistaken assumption that we have already been presented with the "invitation" page and accepted, thus preventing the invitation from ever being displayed, and our browsing being profiled without our knowledge. (I have, of course, deleted the cookie now)