i had this problem as well on my 12C
on my car.....
right next to the quarter panels underneath the hood there is a piece of plastic covering.
it is about a meter long and 100mm at the top tapering to smallish at the headlamp
remove that piece and then you have access to the back of the headlamp
the adjustment head is white nylon 10mm clockwise up, counterclock down(both sides)