well here in america the car is sold as the honda fit, and it's bought exclusively by teenagers and people in their low twenty's. i think it's a great car for a young person. supposedly, it handles nicely, and is very economical.
personally, if i were living in the uk and looking for a small city-car, i would buy the fiat panda. i think it's as spacious as the jazz, it handles just as well, and it's almost £3,000 cheaper. and if hondas really are considered old-person's cars, then i guess this would be less embarrassing.
so, it's up to you. my dad had a 1993 honda accord that had 225,000 miles on it when we sold it back in 2006. we managed to sell it for $1,500 at the time, which is actually a lot for such an old car. i wouldn't be surprised if the car is still running smoothly today. then again, my uncle had one that needed a new transmission at 70,000 miles. every company has lemons.
i have heard that fiat's reliability rating is vastly improving over the recent years, but i don't think they're nearly as good as honda's.
so, it's up to you. do you want to save £3,000 and get a car you feel is more youthful, or spend the extra money and get a car that will be as reliable as clockwork, but is seen as an old person's car.
i think personally i would get the fiat just because i want an italian car.
hope i helped!
good luck!