How old is the car? £2500 sounds about right for a 03 or 53 plate Stilo Abarth with that mileage, any newer than a 53 plate then id be wondering why it's only £2500.
Do bear in mind however, that Abarths are cheap because of the amount they now cost to tax, aswell as being in high insurance groups, drinking quite abit of fuel, and sometimes suffering from costly Selespeed Gearbox problems, so the seller may just have over-estimated how much these things put off potential buyers & put it up for £2500 to get a quick sale.