Wondering if anybody has had any experience doing this
Yes, I've done many like this.
Moving amounts among banks on BT offers is two parties you have to deal with:
1) The bank offering you the BT at a certain fee (or no fee). They want you to move the funds to their bank. They are happy to loan you the money (except Barclays)
2) The bank you are moving amounts off of. You are paying your balance. They don't have any indication where those funds are coming from. They are happy to get their money paid back that you borrowed. (except Barclays)