No heating check programmer
We now need you to check that your central heating is turned on. Go to your programmer and turn it on for the heating to come on and turn your room thermostat on the wall to maximum. This is to make sure that the boiler is being asked to fire up. Some programmers and room thermostats are combined, and some are separate. By putting the heating on constant and the room thermostat to maximum you can be certain that the boiler is being asked to light.
Are the radiators getting warm? You will have to wait several minutes for the chill to be taken off them.
Some programmers are battery operated. Check to see if there are any low battery symbols flashing or appearing on your programmer. If there is, this will stop your heating working properly. You will need to change the batteries. This can also cause the heating to come on when it shouldn't.
Here are some examples of various controls that you may have in your home to control your central heating (and possibly hot water as well).
Danfos TPone programmer and room thermostat. You must increase the temperature to maximum to test. If it's set below the current room temperature the heating won't come on.