dont know what you mean by fabric side skirts but if you mean body side skirts and spoiler its £500 painted and fitted here. not cheap
however you can get the bits seperately for £95 for rear spoiler and £193 for the sideskirt kit.(as listed in my brio magazine)
cheaper to buy from fiat and get someone else to spray them, then fit them yourself, they are apparently only double sided sticky taped on, so should be easy, however they apparently have to be sealed to the bodywork. not sure if this would come in the kit but you could use clear silicon.
im thinking of doing this myslef and it doesnt have to be orderd with the car, it is an option that can be added afterwards.
check he kit is the same as the Abarth kit though as ive heard that there are a few varyng kits at dealers that arent the same as the nice Abart kit.
Fiat Stilo 3dr 1.6 Dynamic, Sassi grey with 17's