black spot

They seem very prone to this Adam.Mine had it last year,I pruned off affected leaves-which was virtually all of them! Then fed with a seaweed based fertilizer in spring.The new leaves were fine and the shrub was lush for the summer-but the same has happened again over this winter.
I would be grateful too if anyone can come up with a more permanent solution !!

Adam, Try 4 rounded teaspoons of bicarbonate of soda to 1 gallon of water and spray the affected leaves. My Dad gave me this recipe years ago and it worked on mine and I have tried it since on roses and it worked for them too........Spray in the cool of the day