I don't have a thermostat. Just have the heating on for an hour in the morning and hour in the afternoon so not sure if it's worth having one as the heating isn't on for long enough to need to be regulated iyswim. Woodburner heats the house in the evening. Do I need a thermostat? I'm prepared to be convinced of the benefits
a stat will bring your home to the temperature you want. So it will not be too cold, and it will not waste energy making it too warm. If you use a woodburner, it will automatically turn off the gas boiler when the room is up to temperature (although it is preferable to put the stat in a different room, then it will heat the other rooms to the desired temperature). Used with a timer, it can warm the house before you get out of bed in the morning.
If your home has never had a room stat, I deduce the CH must be very old, or formerly belonged to an old person who liked to turn the CH on and off like an electric fire.
If it did have one, which has broken, it is very easy and cheap to replace it.
More modern practice is to fit a programmable stat, which warms your house to different temperatures at different times or day and days of the week, should you so desire, to match your lifestyle.
I might get one fitted then. No sign of a stat anywhere. When we moved in it had one boiler for heating and an immersion heater for hot water. Have since replaced with a combi boiler but didn't think about a room stat.