I don't think you can, unless you add a windbreak of some kind to protect it a bit. Our predecessors did that by mounting fine green netting on posts along behind the hedge on the side facing the wind. It's not obtrusive, and does help, i think.

Lichen may not be relevant - it's often found in clean air areas.

Lichen can also grow on branches that are not vigorous or have few leaves. Try feeding it in Spring and also give it a light trim then, to encourage new growth.

There does seem to be a disease killing some privet hedges at the moment.

I've noticed several privet hedges with the occasional dead plant over recent months. I don't know what's causing this .

As yours is coming back then it should be OK. Last winter was particularly hard and privets will lose their leaves in exposed positions in harsh winters. They usually come back quickly in spring.