Thank you very much for the response @dx100uk
Yes, they said that it was the standard rate for my flat. I live in a flat that's part of a building with 3 other flats (old house converted). I said to them I couldn't understand how it can be remotely that high and they just kept saying that is what the rate was.
They are chasing me - Text messages, a recent debt collection letter, then them again. What they've done is roll the entire bill into one so the old £1000+ bill is merged with the meter bills so they pursue me for the overall substantial debt. I just pay the m