At 19000 miles I was told that the rear brake discs and pads were completely worn out.

Fiat says they are wear items so not covered by warranty. The Fiat dealer chief mechanic told me that this was not unusual and that the rears can wear out before the fronts.

I got an independant Motor Assessors report, who concluded that it was caused by one or more faulty components. I asked Motor codes to adjudicate: it appears that they just gave my submissions to Fiat, then took Fiat's reply as gospel and so ruled in Fiat's favour.

Has anyone had experience of similar wear rates for panda discs?

Btw, the car has now done 40K miles - the original front discs are still not worn out, and the replacement rear discs have now done 20K and are barely half worn.