What you actually need is a house move but move your existing package to a new second line at an existing address. However, I'm not sure if such an option exists perhaps @-Richie- might know.
It's a possibility yes, that was why I wanted to know the desired outcome.
Installing a 2nd line leaves Grandad's unchanged and allows the OP to have their own connection.
You've been offered moderator support, I'd advise taking them up on the offer.
You want a home move but to install a new 2nd line at the target address, it's more complicated than a normal order and there can be extra charges for the new install, depends what the survey picks it as each property is different.
Thanks for you help. Yes, a moderator has private messaged me and someone will hopefully be contacting me over the next few days. It's been good to find out exactly what I would need to ask BT to do and to find out that it's possible! So thank you to everyone who has taken the time to reply to me, it' s been really, really helpful.
Thank you for taking the time to chat with me again this afternoon.
I am really pleased that I was able to help you move your services to your new address. I am sorry for the confusion prior to my involvement.
As this is sorted I will go ahead and close this off from here, as agreed.
Enjoy the rest of your day. Take care.