What you describe sounds like windburn, and that can't be repaired. Maybe the whole of the tree won't be damaged but I think the best way forward, at least for the time being, would be to plant a climber that can grow up through the trees and cover the bare patches.

9 conifers but you don't say what type. Are they all the same or different species?
Depending on the species, they may recover after a few years if you remove the brown/dead patches. As Silverbelle says it may be windburn or it could be due to a lack of water.

Thank you both. I too thought about putting a climber by the trees in the hope it would grow up through the brown patches. I like the idea of a Clematis Montana as I love the pretty white flowers. Would that be OK by the trees. I'm really a gardening novice so all your tips and advice are welcome. I have no idea what type of species the trees are - they look like bog standard conifers to me (like I say, I'm a novice :-)