I'm not sure what you mean by migrating to a new copper pair.
Do you mean obtain one, (from which supplier?) then migrate the broadband to it from the existing one? Your current broadband or a newly established AA one on the existing copper?
I just can't picture the sequence that doesn't result in a full broadband cease. As opposed to the instant cease and reprovide that occurs on migrations to and from non-BTW connections.
Ah, re-reading, you mean new line from AA, then migrate the broadband to the chosen product on that line? That might work. Which ISP are you with?
Note you could also stay on BTW on the 350GB option, costing a fiver more than the 1GB TalkTalk business one, if you would feel safer. Or go on the 250GB and risk the occasional £10 for an extra 50GB with carry-over to the subsequent month.
Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - AAISP Home::1 80/20. Sync 65702/13958Kbps @ 600m. BQMs - IPv4