I won't write an essay about the ordeal but key points below:
Incorrectly billed me for 18 months despite multiple complaints to them
telling SSE to review my account
Tried to demand 1.5k of back payments and threatened to install a pay as you go metre, this is despite the account still not being corrected
Took them to the ombudsman who sided with me and awarded compensation but it still doesn't make up for the hell they've put me through for 18 months.
Avoid at all costs but if you're a current customer then go straight to the ombudsman. They will try to prevent you from doing so but the best decision I made was taking it further, I wish I did it sooner.
I hope ofgem launch an investigation as I know I'm not the only one.