Has anyone here had experience of what looks like die-back in a holly
hedge?

We are seeing what I think is an increasing patch of die-back in the
hedge I look after; the garden is one side, a quiet rural road the other
side. Hedge he
http://tinypic.com/r/dpj0k2/8

Close-up of leaves here -- though you can't see much, except that they
are dead:
http://tinypic.com/r/2r2sr9f/8

I'd like to know what I can do about this -- if anything.

John