I have managed to Change My Email Passwords and it's working good for me now.
I dare say Everyone who is having major issues probably has a second / foreign account copying everything out via IMAP. I am sure it was IMAP because some of my messages kept going from read to unread and that's either a server issue or has to do with multiple IMAP users.
I am open to withdrawing such a claim if a VM bod in the Know will say it's not a large hacking attempt.
If no "App Password" is set up in your email then do that and it appears to log out existing logins.
Try changing your password and then see if ti works. If it's not the primary account then opening up https://www.virginmedia.com/my-virgin-media in a private browsing window will let you log into the email in question (it shows up as a whole account, but with account info from your main account).