Re: 156 headlights - protective film?
Was it like a lacquer coat? If it was, what you have probably removed was the hardcoat that is applied to all polycarbonate lenses to protect them from scratches. Polycarbonate is very strong in impacts will easily survive a stone hit (it's what they make bullet proof screens from) but is very soft and will scratch easily.
The hardcoat is applied during the lens manufacturing process and is there to stop the lens scratching. Scratches will cause glare to oncoming drivers and will also scatter much of the light thereby reducing the amount of light that gets onto the road thus reducing the amount that you can see.
If it is the hardcoat that you have removed than unfortunately there is no way to repair it as it is a specialist lacquer that is not available on the open market. Best bet would be to get some replacement headlamps off *bay.