The joystick to control the mirrors.

They differ a little in operation over the various model years of the Fabia I think. Can I however use any control kn0b from any Fabia on any other Fabia... or does it have to be the right kn0b for my car??

I know that there are various types for the Octavia. Your best bet is to remove the old one and there is usually a part number printed on the back and replace it with one of an identical part number.

No they are different as I had a problem with the one on mine and bought one that was slightly different and it didn't work!!! Then bought the correct one from Skoda and that worked fine.