It's rare for us to have the gas heating on, in fact the main cost of our gas is the standing charge. It's only ever used for an hour or two when the house temp dips below 12oC.
As we both like it cool, we tend to like it about 17-18oc. Anything above 20oC feel too warm. Due to that we have a multifuel burner that runs from Oct-Apr, in the milder months it will be on of an evening, with colder months when ever anyone's home for the day.
Due to an open plan house, it heats the living areas nicely to 18oC and takes the chill off of the rest of the open plan.
If there's free wood it is of course free heating, but we usually spend around £200 on cordwood that I chop and store (around 9m2) and then maybe £50-100 depending on how cold it gets on smokeless coal a year.
We don't have any heating on over night all year, it's chilly getting up, but once in the shower we're only 20 minutes away from being out of the door for work.