That link is confusing and i understand the reg plate system. Basically the 5 means September and the 9 means 2009. So car was first registered in September 2009.
Registered some time between 01/09/2009-28/02/2010
Fiat certainly should be trying to sort the troublesome cars out as a matter of goodwill but doubt they will.
What do you expect them to do? It's no fault of the car if some idiot buys a diesel and expects to do only 2-3 mile journeys every time they get in it. It's user error, not Fiats.