Privet hedges dying

[dartagnon]

The middle section of our large privet hedge has lost all its leaves and appears to be dead. Where the leaves used to be there is a grey/green fungus growing on the twigs and branches and down at the base where the hedge root meets the ground it's covered in a light green powder. It has started to spread to the hedges on either side and their roots also now have this growth.
I looked at earlier answers re Honey Fungus and the photographs on Wikipedia don't look anything like what's affecting my hedges.
Any suggestions as to what this growth is and any links to photographs to confirm would be appreciated.
Thanks in anticipation.