That repair is impressive.
In this instance, how mucch is a complete used headlight compared to only the lens?
Too late now yes I know, but.....I soaked the headlight securing nuts in PlusGas daily for some days, well over a long period actually because I had the time. And they undid easily. It is I think making part of servicing to apply penetrating oil to those nuts.
And, yes, use grease when assembling. Copper based grease on mine now.
If working on the headlights, probably bst to change both reflectors. And so far as I can see Charlton lits are complete with the both white plastic anchorage clips and the metal clips. Mine were, from Charlton a couple of years ago.
Be prepared for at least some metal clips to fly off in directions.
There are two additional metal clips, one per headlight. They are the headlight wiper stop fitments. They are worth some anti-rust treatment while doing the job.
I found new reflectors transformed the headlight performance for the better.
Enjoy the job.
.