Both high and low beam adjuster on my 2005 S-Type do nothing. I understand there is a "screw" into the housing method to lift the headlight beams upwards-mine point nearly to the ground at this point!
But is there a way to do the screw mod to adjust either high or low beams independently?

 

You can usually find replacement adjuster kits on EBAY ?

 

The high, and low, beam height is determined by the angle of the one-piece reflector unit within the housing. The single screw through the outer clear plastic lens will/may help to adjust the angle of that reflector, but was unsuccessful on my headlamp. I took it apart and used one of the adjuster kits from eBay, as referred to above. I used a heat-gun to soften the butyl (I think) adhesive in order to separate the lens from the back of the headlight and took it from there. Once you are in there the procedure is obvious. The main effort comes in the removal of the bumper in order to remove the headlight. You could look for a second-hand headlight so that you can replace the broken unit straight away, but be aware that by now - 20 years on - the plastic adjusters on all of them will be fragile. Maybe do what I did and re-furbish a second-hand unit beforehand so that you can replace your broken headlight as soon as you remove it.