That does seem exceptionally high.
We have oil central heating, which with current oil prices should be higher than gas and in the last 12 months, we have spent 1400 on oil.
When you talk about your zoned system, does this mean that the thermostat in the system always decides whether to turn the heating on or not.
Amybe these are obvious questions, but how does your zoned system work ?
Do you have a timer to override this, for the night-time and when the house is empty ?
How many hours a day is the heating on ?
Surely it is off completely in Summer. Why would the heating be on at all in summer.
Maybe the thermostat is set too high.
Is the thermostat controlling the heat at night ? If so, are you heating the house all night ?