robin69 Virgin Media now require you to use a generated app password for access to their email accounts when using email clients or apps.
VM have recently changed the log in requirements for accessing VM Mail via third party apps.
If you change the password for the account in My Virgin Media > Account settings > Account details you will not be able to use the new password to access the account via an email client. Email client access now requires an app specific password which can be generated in the MyVM > Account Settings > Account details > Mailbox App password management
You are likely to be asked to change the username for the account to a third party email address during the process of getting the app password. This doesn't change the underlying email address just the way you sign in via My Virgin Media or VM webmail.
You should continue to use the full Ntlworld email address as the username for your mail and but with the generated app password.
https://www.virginmedia.com/dpb/help/change-my-virgin-media-email-address