I know this is boring, but...I'll feel better.
My Scottish Power complaint finally resulted in them agreeing to stop billing me for gas I hadn't used and standing charges on a non-existent meter at my permanent address, the removal of which had been arranged with their involvement.
Of course when they emailed to say the balance was now zero and there would be no more demands, I knew that that wasn't the end of it.
How? Well back in November, they told me they could not deal with my complaint unless I ran a Direct Debit indemnity claim for all monies debited to me by Scottish Power after 9/4/19. I questioned the need for this but they insisted. So I did what they asked, and I got £1860 back.
This wasn't surprising as I had been with SP for about a year at my temporary address so most if not all of the £1860 will have related to that. Obviously they were going to ask for it back. But they didn't.
Then this morning I had a call from another debt collection service. Other than mentioning Scottish Power, they wouldn't discuss what they wanted because I refused to give a cold caller from a business I had never heard of my DoB. We had the usual idiotic requests for me to "confirm" details which I offered to do, but of course they meant "disclose". I had already given my name and addresses but I declined DoB.
I have emailed SP and told them to let me have an account and reference so I can pay back the money; and that they don't need a debt collector, they just need to ask.
Never, ever get involved with SP. If you are, switch providers before your house burns down.