Thanks to ap0gee's 'how to' guide I replaced the sensor on my Fabia. The text and particularly the photos were especially helpful, though there were real problems locating the sensor and withdrawing it. This last step was only possible for me by using a dental-type inspection mirror and inserting a small short screwdriver down the side of the plug and breaking the plastic retaining collar. As you suggest, if only the wires from the loom to the plug were 5cms long instead of about 1cm ...!
The AC now works well, though with everything set for maximum cooling the air from the ducts measures (eventually) around 2 degrees on a thermometer placed against the vents. This seems low in view of the figures you quote in your reply to AFAIK.
One last query - just to show my ignorance - what is the function of the switch operated by the clutch pedal: this is the one which has to be removed to do the sensor replacement.
Very many thanks for your help - without which I would not even have dreamt of attempting the task.
Allan
PS How do they get to the sensor in a Skoda workshop?