An official FAQ reply from Microsoft reveals that if you have ever been on developers preview and later opted out of it or have been removed from the program, you wouldn't receive the "Lumia Denim" update or will face the error 8018830f while trying to update.
Solution suggested is enrolling back
Seems while error #8018830f has been fixed and it has confirmed by many of our readers now, the error 0x80188308 is still giving trouble to some of the users.
Thanks Brian for the screenshot!
Few of you have tipped us that the error #8018830f may have been fixed by Microsoft already. This