Seat Ibiza - Cordoba 6L 1.4 cc BBZ VAG engine - How to remove and replace thermostat

Once a while it is happening to every car.
The thermostat fails.
This is the replacement on a Volkswagen - Audi 1.4cc engine with
the code number BBZ which can be seen in a lot of models.
The Ibiza,Cordoba,Fabia,Polo,Golf etc of the mid 20`s could have this engine that produced 101hp.