calamity jane,
If you haven't got storage heaters and don't use more than 20% of your energy at night i.e. 1am - 8am, then I'd advise you look at changing your meter to a standard credit meter.
This should come at no extra cost and can be arranged by contacting your current provider direct. Simply advise that you want to change your energy meter and ensure you check whether or not there is a fee involved (there shouldn't be).
If you do not have storage heaters to run during the E7 hours then you are paying a higher unit rate for your energy during the day than you would do on a standard credit meter tariff.
Hope this helps.
Regards,
Scott Byrom
Utilities Manager
moneysupermarket.com