 Re: Npower
This sounds a little tricky. I don't know the answer but here are my thoughts:
The previous owner / occupier should have given npower a meter reading when they moved out, which should have corresponded with your reading when you moved in.
If they didn't, npower should have been able to estimate the expected meter at that time reading based on the previous person's usage.
In my opinion, when you gave the reading from the wrong meter, that should have raised alarm bells at npower, they should have asked you check again (after all, you are not a meter reading, they would know that the reading was for a flat and that there might be several meters that could cause you to be confused) [I know of cases where the electricity companies have been reading the wrong meters for several years].
You could suggest that they have failed to exercise due diligence in accepting a wildly inaccurate meter reading. You could also argue that if the previous people did not supply a reading when moving out, then there was even more reason for them to pay particular attention to the reading that you gave.
It is quite possible that npower have charged the previous occupier up to the correct meter reading and have been paid twice for the same electricity. They might even claim that it is against the data protection act to even look at another account to see what has happened. If you know the previous people, they might know if they read the meter before moving out.
There may be something about the previous person's liability that other people might know about.
I can't believe that a utility company is saying that they are unable to estimate a bill - they do it all the time.
Estimate forwards from the last reading from the previous person based on their average usage, do the same thing backwards for you and see what the results are like - how much of a difference there is between the two results.
How did you come to realise that you had read the wrong meter? Was it because of the bill or something else?
Grumpy | 
