Call some local Fiat dealers and get their LABOUR charge only.
That's your benchmark.
If they say £250 , and a local mechanic quotes more, you'll know you're being done. As the dealer never usually does it cheaper.
This happened me a few months ago, now when I want pricing I set all quotes against Fiat. Sometimes it's just a £40 difference and with a 2 year guarantee Fiat seems tempting!