Ride is just right on normal suspension. Taught, but you keep your fillings. If you are going to track the car, then the sports pack might be right. But I would not understand any other reason for picking that option for British roads. And remember there is no going back once you have it!
Dual clutch works well, nothing to worry about. Keep your foot down and click away. The 4C paddle shift is somewhat annoying as it sits on the steering wheel rather than the steering column. Drive around a roundabout and you will see why this is an issue! I have resorted to dropping into Auto when confronted with low-speed roundabouts.
I have no problem with the seat - I'm 5'10" and medium build - but others have complained about it. Seat height has to be adjusted by the dealership, so best to get that sorted before collection. Getting in and out of the car is an art, and I would not like to have to do it if I were either taller or heavier than I am!
If you have chosen the stereo upgrade as an option, then cancel it. Waste of money. In contrast, the paint upgrade was worth every penny. It's stunning.
I imagine the lead times on spiders are not appealing, best to check them vis-a-vis the regular 4C. Alfa have had a tough time in delivering 4C's in a timely manner to their customers, much to the frustration of the dealerships. If I weren't a dyed-in-the-wool Alfa and Maserati fanatic, I would have bailed out and got a Cayman instead as I really did not enjoy the fact that neither the dealership nor Alfa Romeo themselves could give me even a roughly accurate delivery date.
No doubt you are dealing with Simon at Wessex, he's a class act and will give you as good if not better advice than I. He's spent a fair amount of time behind the wheel of 4C's.