With regards to the OPs issue, what I can't figure out is why he didn't phone Fiat/Abarth UK regarding a contribution to repair cost before going anywhere near a garage
Yeah it's out of warranty in terms of time, but it's not out in terms of mileage and the warranty terms suggested the problem would've been covered in year 3 when many things are excluded, so chances are they would've entertained a goodwill claim. They reimbursed me with vouchers to the full cost of repair when my Stilo's suspension springs snapped at 6 years/60,000 miles, so never assume they'll say no.
Also, if I was being charged north of a grand & got told there was no courtesy car available, they'd have been told which finger of mine to swivel on. To then appear unable to do the job properly suggests to me they're having a laugh and you've been mugged off. I hope to God this isn't an Abarth dealer? If it is, I'd strongly suggest calling Abarth on 00800 222 78400. They're seen as being above Fiat, so you'd hope you get some sort of preferential treatment for paying the premium over a regular 500.