Which branch of Ancaster - and when you say they are not being helpful, what are they not doing?
I'm sure that if they have been the main servicing dealer as well, especially if they supplied the car, I'm sure they will support you in going to Fiat.
Honestly, I'm sure Fiat UK will help, just be fair and reasonable, don't argue, just look for their support, and ask if they feel it is reasonable that the failure has happened?
At the end of the day, we all have a choice in these situations, i.e. once a car gets to an age, do we extend warranties etc... to give peace of mind.
Cars shouldn't go wrong, but the fact is they do, some from day one, others never go wrong.