You cannot 'change' an email address, an email address is unique, you can create a new one though.
Once you have created a new address you can make that the primary if you wish to.
It won't, email addresses are unique. Mail sent to your old address will arrive at your old address, mail sent to your new address will arrive at your new address.
A 'Primary address' is just the address BT use to contact you and the address you use as an account holder BTID.
Yes, I tried that but it doesn't replicate the existing email account with everything in it that I need - folders, etc.
Is it not possible to simply copy the folder structure over from one account to another?
Of course that depends if you are using webmail, or an IMAP email client like Thunderbird, which will allow you to do that very easily. I am not sure that is possible on webmail.
Of course not. They can only create a new address with their new name if they so wish.
Why do you need to change it, it doesn't really matter that it contains incorrect information. At the end of the day an email address is just a string of letters and numbers.
So if someone changes their name (say gets married) they can't change that on their email address?
They can change their name, but not the email address - it might already be in use.
I know a few people who use a similar method for their email address (part of their home address!), so if they move their options are to keep it as it's only an email address - it doesn't really relate to anything else, or create a new address and use that.
To me the easiest thing to do is nothing 🙂