My alternator died last week sub 4 yrs old lc gs with 32k on clock - dealer 1st said no way was it the alt as they have never had to fit one but hey they were wrong. Just my luck. Anyways £1500 min to sort!!! engine & gear box out, my mates got a ford kuga £300 for a new alternator. Bmw sort yourself out.
Oh & then there was the flapper jobbie in the exhaust, when that seized it was £1200 for a whole new set of tubes, coz guess what bmw don't do just the small part, bmw sort yourself out. I'm supposed to be mile munchkin circumnavigating the globe not poncing about in the garage skinting myself, I coulda bought a Honda for that.
I would be examining the failed alternator, if it's bits rattling around in it possibly an assembly fault.? I would be asking for a bit of goodwill on that depending on where the fault lies..
Good luck