As far as I know both accounts can sign into My Virgin Media, and then there is an email login box at the bottom of the page. A secondary account in My Virgin Media wouldn't see a lot of the account details though.
Just an update. It seems the new VM homepage has changed to an advertisment for the new Batman movies. You have to click on this homepage to get through to a second screen which has the email link. Seems a bit convoluted to just get through to the correct page.