I have glued the electrical ones on Iveco Daily so they would still adjust.
Is it the up and down or the left and right adjustment or both , often just one gets a bit brittle. What happens is once it breaks away the reflector inside the headlamp can flop around.
I have an old Citroen AX and my neighbours Peugeot 205 headlamps are very similar , just a slight curve at one end to match the wing shape.
Presumably once they are in the correct position to pass the MOT then there would be little need to move them again, although I have had testers who used to adjust a headlamp every year if they could find nothing else to fail to give something to charge for

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If you can chat to your Mot tester and ask for his advice explaining the situation he hopefully will use a little commonsense, though it may be an idea to look up the Ministry of Transport /DVLA regulations regarding headlamp adjustment before hand.
Theoretically if you mounted a couple of tractor headlamps on the bonnet at the correct height , giving dip and main beam etc. correctly aligned it could meet legal requirments, though I am not advocating that

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