Thats a shame. I've had mine since early December but only put around 300 miles on it.
Its brilliant. I've not had a car with a limited slip diff before but the way it corners is surreal. Suspension is firm but smooths out bumps so well - not crashy or jarring as you might expect a firmer ride to do. Plenty quick as you'd imagine for 260bhp - loads of low down torque. It feels like its egging you on to go faster / harder all the time - like a coiled spring.
Coming from VAG gearbox's - or rather VAG software controlling the gearbox - it is very responsive and I would say the changes are very well judged in all the different driving profiles. Not too early in comfort, about bang on with the car in 'sport' but gearbox in 'D'. Gearbox in 'S' naturally revs all the way to the top. Its not perfect but very good.
Brakes are very sharp on first bite but then not as servo'd as typical in VAG cars. Not sure if thats good or bad tbh. Just different.
Fit and finish is excellent, very 'premium'.
Negatives - access to the rear seats isn't as good as a Golf. All the seats are closer to the floor than in a golf and this combined with a sloping profile to the roof makes it a bit more difficult to get in. Doesn't bother me but it could some.
Virtual cockpit isn't as good as VAG implementations but you get used to it pretty quick. Main infotainment screen is very good though. I don't have the HUD but those that do swear by it.
The recommended tyre inflation pressure is very high - 2.7 Bar at the front - seems to be a common BMW thing. I still need to reduce that a bit further.
If you have any specific questions feel free to ask. I can't imagine you would be disappointed by either the GTI or a 128 to be honest.