I entered the site by pressing the "My Virgin Media" tab at the top right of their main page at http://www.virginmedia.com/
You ask why they would need to confirm my details.....I wondered about this too. The only explanation I can think of is to force you to accept their spam.
No one at VM could give a reason and as I worked my way up the food chain of CS the more difficult it seemed to get.
I was left with the impression that I was the only person to complain about the web page in question, and told in no uncertain terms that VM were fully compliant with OFCOM regulations and that I should adhere to the T&C's and not complain to CS but to write a formal complaint.
Don't get me wrong, I think Virgin Media provide a very good service, however, when something goes wrong and you try to work your way through the CS system it seems they have very little interest in the customer. Perhaps I'm just too old and expect too much?