If you've already bought the car,and signed for the finance, then it's surely immaterial whether it's a good deal or not?
Manufacturers' finance is rarely going to be a good deal- but nor is buying a car brand new, as you'll lose the VAT element (20%) in the price as soon as you drive it away, then you will suffer the first few years of horrendous depreciation,all of which losses you must stand......
The BoE interest rate is a nominal 0.5%- try finding anything near to that! BUT, a bank loan is likely to have been about 4%,as opposed to FIAT's 7.7%.
A bank loan would ,if in place, have allowed you to negotiate hard on a "nearly new", ie pre-reg'd car with only minor mileage ( my last "new" car showed 12 miles and was weeks old) --- the VAT element has been already "written off" against tax by the dealers, and the first year of depreciation has already come off the value as it is no longer a "new" car. Or,perhaps a better deal might have been available on the "new" price. You would also then have been the "owner" of the car, rather than the "hirer" as you will be until you've made your final payment or handed it back to FIAT.
IF you wish to dispose of the car whilst on Hire Purchase/ Personal Contract Plan, you'll need to settle the finance first if you wish/need due to unforeseen circs to sell the car lawfully- though SOME unscrupulous persons sell the car, with the promise to settle the outstanding finance afterwards, some don't even do that and unless you HPI check the car you may not know if it's financed.
The manufacturers hope that you'll become, effectively, a permanent "hirer" from them, and change your FIAT for another of their cars,again on a PCP, before reaching the stage of making the final repayment.
Whatever, I wish you much enjoyment of the new car- that feeling/smell of a brand newie is great........................