There are two variants. One has the basic light sensor, which is mounted on the top of the dash under a small plastic square. Higher spec models have the one mounted in the rear view mirror mounting.
If you go on the Skoda Fabia price list you can see the difference - configure an SE model, and you can have Light Assistant for £85, or Light and Rain Assistant (which includes the auto dimming mirror) for £220. The pictures are irrelevant BTW!
The new Polo and Ibiza both have the Light Assistant as standard on base models, and then the more upmarket cars get the full sensor cluster. Any car with climate control which also has auto light I *think* gets a full light/rain sensor, but don't hold me to that. Certainly any car with climate has a sensor mounted up there, for the humidity.