Councils tend to be very strict and are charging punitive rates. I understand that if you leave it for 12 years there is no charge. She can try negotiating but in our area it doesn’t appear to work.
I purchased a derelict property in 2012, it had not been lived in for about 20 years, I have photos of how it was when purchased and I got an exemption for LPT. NPPR was never paid on it, any point in going to the County Council to state my case?