I got it running, finally. With a HUGE workaround.
- start with the live CD
- open a terminal and (optionally) examine the local drive with fdisk
- use parted to remove all local partitions
- install (beleve it or not) F10
- then install F12 over that
That was the first time it asked a confirm on the bootloader.
If anyone has the same *** with the install, this _could_ be a way out...
Only hope I could help (for a change) instead of being helped
(and again: seasonal greetings)