I and my wife have a similar problem. We were Virgin Media customers for over 10 years, and still have Virgin Mobiles. When we moved house 3 years ago we were unable to keep our Virgin Media accounts (it is not available in the area where we now live). Our Virgin Mail accounts both seem to have been disabled this week - I'm guessing as they are 'orphaned'. Please could we have temporary access to them to transfer emails to our new email accounts?
David_Bn is correct, VM will not assist former customers except to completely delete a lingering email address.
Just to be absolutely sure go to mailtester.com, and enter your email addresses. If they come back as live/active/whatever then you might be able to access them using an email client like outlook or thunderbird until they are permanently removed from the system. (webmail access is the first thing to cease).
But if you do get access and back up your data, be sure to request that Virgin complete the permanent deletion after that. There are so many cases of people having these orphan addresses hacked and their personal data misused, I wouldn't want that to happen to you.