OK... That seems to have worked!
I didn't anticipate that I would get a notification for every single follower that got re-connected with my new account, so my browser went "blip" quite a lot over the last few minutes. 😆
I used this guide to accomplish the account migration - it's great:
https://codingitwrong.com/2022/10/10/migrating-a-mastodon-account.html