Hello all, third post as a member and straight in for help - a good sign?

Currently in the process of restoring a '87 Aircooled 126. So far, not too bad.
(More info on the jobs done so far :
http://club126uk.co.uk/smf/index.php?topic=8821.0 )
Almost at MOT stage, bar a few small bits n bobs and one BIG headache...
Side lights - OK.
Dipped - zilch.
Full beam - OK.
To explain in a little more detail :
Flick the switch in the cabin to position one, side lights come on, rev counter illuminates.
Flick switch to position two : side lights flick for a millisecond, remain on, but no dip lights.
Pull full beam stalk to flash : full beam flashes and dash telltale illuminates.
Lower full beam stalk for continuous light : nothing, no telltale.
Headed to fuse box - the wiring is all in good condition, fuses intact.
Bulbs all in good order, connections good.
Rear lighting working correctly.
Confused.com!
3 weekends later, a lot of head-scratching, a lot of googling, a lot of nothing!
Does anyone have any tips / info or, ideally, a bit of info on what each fuse holder controls and what is supposed to enter and exit each respective fuse (I'm querying this purely cause the car came to me in 2000 bits and am slowly piecing the jigsaw together, with help of Haynes and Autobooks, though admittedly - the diagrams in their books are not my strong point!)
Many thanks in advance!