British gas electricity supply

I have just received a bill from British gas for my electricity supply which is 4 times the usual amount, despite the fact that nothing has changed in my property. There is only my husband & myself live there and we both work full time. On average I use approx. 13 - 15 units per day. Checks on my meter have verified this. However, my last reading showed usage of 51 units per day! I have spoken to all lines of communication at British gas and their suggestions, but no one seems to be able to identify the possible cause. If it is something we have done, then we are prepared to accept this, but I genuinely believe it is not. I just need someone to help explain this huge jump in usage (& cost).

Regards,

L. Brasted.