It's possible that VM have charged for the delivery which is wrong as the email does state free upgrade.
Hopefully a member of the Forum Team will pick this up for you in a day or two, rather than you having to contact billing.
Upgrade for free to Virgin TV 360
You have some of our older TV equipment, which means you may not be getting the best TV experience; like our new service, Virgin TV 360.
It won’t cost you anything, we’ll just send you a new remote in the post and then complete a software update to your existing TV boxes. Virgin TV 360 will allow you to access features and apps (such as Disney+ if you are subscribed) that are not compatible with your current TV experience without any need to change your current package.