What sort of heater are you using? Our electricity bill rocketed two years ago and I had a heart attack when I saw it. I rang to query the increase and they listed a number of things that could have caused it. One of them was a heater we had given to us when the conservatory was built. We were initially told it was cheap to run as it was only a 3kw.
However, on speaking to our Electricity supplier, I discovered that a 3kw heater means 3 units per hour. At the time, I was being charged 6p per unit, which meant 18p per hour for each hour of use. During the winter, the heater was on for 5-6 hours during the evenings and pretty much all day at the weekends (kids homework, computers). At best, the heater was costing us an extra �1.00 per day! It all adds up.