Thanks for all the advice, in answer to your question the house is a five bedroom terraced property built in the last thirty years. It is heated by gas and our gas bills have always been low. Our electricity bills have always been very high though which I put down to the fact that we have a large family with a lot of washing, and the tumble dryer gets used a lot. Three years ago I used uswitch to change suppliers and we went with npower for both our electricity and gas combined. It's only since we have been making a real effort to cut back on our electricity use yet at the same time saw an increase in our bills that I realised there might be a problem.

Npower is sending someone out to investigate but we will have to pay a £70 call out fee!