A powdery white coating appeared on some leaves of my laurel bushes last
year, and it has started to appear
again this year. The affected leaves curl up. The bushes are about 15 years
old, and are in the south east UK.

There is a picture of some affected leaves here
http://ucosm.tripod.com/photos/laurel.jpg

I suspect that it might be powdery mildew.
Is this the correct diagnosis, and if so what should I do to cure it?

TIA
Sue