Anyone else experience problems with the rear demister not working?

Light coming on at the switch on the switch

With the light coming on I would expect the fuse to be intact but worth checking. It is fuse 25 behind the removable cover on the driver's end of the dash. Note that RHD drive cars have fuse locations shown the opposite way round to those on the diagrams.

 

Often the cause of a failed rear screen heater is scratching of the heater element lines, so breaking the circuit. The usual reason is that the boot was overloaded (by such as garden waste or cardboard boxes) and rubbed on the glass.

You can confirm with a multimeter the 12V is or js not getting to the screen. You may need to remove the hatch/boot lid to access the connector.

 

It is always helpful if you can give year of manufacture//pre-facelift or facelift//hatch or estate//trim level//engine code as a minimum.

If you need a driver's handbook for your year you can download one from the pinned post at the top of the list of posts.