With this I get presented with the sign in box, enter my credentials, it sits there for a while and then redirects to store.virginmedia.com and I get a message saying that my mailbox is unavailable and I should try in about an hour.
From my Android devices I ham using the Gmail client connecting via IMAP as I have done for years with my 'ntlworld' account added. Nothing was changed on either of these clients my emails just stopped working
This complains of 'Correct Credentials Needed'
I enter the correct credentials and hit next the email client then comes back with 'problem with account setup - Your username or password is incorrect'
If I go into the settings of the client I can update the SMTP settings without issue. It's just the IMAP settings that won't resolve.
Three other members of the family with emails setup under the same account have no issues and I have no other issues as I am currently working from home and can quite happily connect to works systems via VPN etc.
I have tried the link in the thread you refer me to after clearing my cookies and history in my Chrome browser. I still get directed to store.virginmedia.com/unavailable with a message saying that your mailbox is not available at the moment - try again later. I have spent most of the day in an online chat to Virginmedia regarding this issue and have have been assigned an IT ticket reference number P009983837.