I mistakenly knocked and broke off one of the rear window defroster tab. 

Repair looks quite straight forward in some other car models, but Fabia has it enclosed in a pillar.

 

So has anyone repaired this before, if so how did you do it?

 

Thanks for any advice.

I think what you are seeing there is a straight forward bayonet type fitment. You may be able to just pull off the broken tab from the clip that is coming out of the rubber grommet. You may have to have the tab re-soldered then clip it back on!If it is un-solderable, you may have to fit a complete new heater element but thats not too likely unless you can't solder or get someone to do it. Its as likely to be just as difficult tp replace the lot as its most likely stuck down under trim parts. Take care not to damage more thing though!