There is no timer in a storage heater.
They are designed to come on at night so that they heat up the bricks inside them using the cheaper rate of electricity at night and then they release the heat that they have stored slowly through the day.
If you are needing extra heat then you either need to turn up the storage heater so that it stores more heat at night or you need to buy an additional convection heater that you can turn on as and when you need it.
Rick, February 2008