Jon,
Welcome to ECN, mate!.
This sounds really ridiculous, I think that you either have a grossly faulty meter(your local Power company should be able to check this for you),or, the person who done the estimate has really mucked up.
One question,Jon,are you estimated power accounts, based on the usage in the same month of last year(ie: 12 months ago)?.
If so, I would personally look at what the last person who lived in the house was doing with all of the Electricity!!. [Linked Image]
An on-going electrical fault can cause the meter to spin like a Helicopter rotor, especially, where the fusing is over-rated, although the cabling is larger than what is normally required, it's a bit of a pipe-dream,but it can occur.