The DD kill switch was more of a Peacock moment, but you're right on that. It would be stupid.Perfectly normal, it should have been explained as part of the disconnection process, assuming you spoke to someone. Basically the billing system will bill you as normal, once your account disconnects any advanced payment is credited back and a refund cheque issued, but it'll generally be 3-4 weeks later by the time you get it and if you have moved, I hope you supplied a forwarding address. Cancelling the DD will result in a failed payment being reported... that would be self-inflicted stupidity.
It got me annoyed as expected a £6 plus bill as that is what the woman said would come through today as my final bill. I've read a bit more on it so looks like she was wrong.
They didn't explain anything about a cheque and no I haven't moved. You'd think they'd bill me properly for the pro-rata amount. I really can't wait to be rid of them.