I live in a rented house that has gas central heating, but it doesn't work very well. Its always very cold even if we have the room thermostat on 25 or 30. When turning the thermostat it never clicks higher than about 20 even if we leave it set higher. For example, we can have it set to 25 all evening and the boiler doesn't come on and it only clicks at about 20. Recently had it all checked when the plumber came for the annual gas safety check but he couldn't find any problems and has no answers.
The thermostat, motorvalve or pump could be faulty or system could have an air lock. Check that the boiler is set to 80C and that any thermostatic radiator valves are open and not sticking. Ask the landlord to get it sorted.