put in my email address and then got a really weird screen where it asked if I wanted to allow a code numbered device to have access
That sounds as if you were diverted to Virgin Media's new device authentication sign in process. See here for details https://www.virginmedia.com/help/account/what-is-device-authentication
If you are using a device that supports face or fingerprint authentication that enables you to sign into VM without entering your password. You can set up a number of different devices (for example your iPhone and your laptop) if they have biometric recognition and that was the code that was being requested.
If you have not gone through that device registration process it seems strange that you were asked for that device code.
I used to get prompted to register my devices every time I signed in to VM but I just kept ignoring it and entered my password as normal and it no longer nags me.
You can try this link to sign directly into your VM webmail account https://mail2.virginmedia.com/ or use this link https://virginmedia.com/my-virgin-media to sign into your My Virgin Media account. Certainly when I use those links I am not prompted to sign in via the device authentication route.
I hope that helps.
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