Mildew on my Laurel Hedge

I have a 6 foot (tall) by 12 foot (wide) by 3 foot (deep) laurel hedge that runs along the bottom of my front garden that is well established from when I moved in my house 7 years ago.  It affords the front of my house a little bit of privacy.  Every year it gets a trim in August/September to keep it in a relatively tight oblong box shape. I like it and I wouldn't want to lose it, however, every year it suffers really badly from mildew to the point last year almost all the leaves had shot holes and it looked very unsightly.

This year I decided to spray the whole hedge with fungicide and although the mildew is not as bad as last year the hedge is still looking really sorry for itself and the leaves are still mottled.  I am wondering if there is something else going on like leaf spot fungi, however, I would have thought what I sprayed would have treated that.  I only sprayed the hedge once and wonder if I should have sprayed it more although the instructions said spray it no more than twice in a season.  I did not spray until I noticed the mildew and wonder if I should have done it before any sign of infection.

New growth that is coming thru' this year is seemingly unaffected, but that will come off when I trim it back to its tight shape again in late summer/early autumn.

Can anybody offer any top tips on how to get rid or really reduce the incidence of mildew?  Should I have sprayed earlier in the season and if so, when.  I think I remember spraying it in June.  

In terms of location.  It is a fairly hot and dry location specially in summer and the ground always seems dry under the hedge.  I do regularly clear out the dead leaves (and there is often a lot) under the hedge so that keeps the air flowing and also any rain that does fall might soak into the ground and not just on the leaves.  The soil is a light loam.  I'm thinking that given that is so well established, that water is unlikely to be a major issue.  I don't water it especially and I've never fed it (perhaps I should?) 

Anybody offer any advice?