Is this leaf spot/blight

[groucho]

I have noticed a lot of the leaves yellowing and dropping from my Hawthorn bush. Is is as the title suggests? If so, what can be done?

[Mr GrimNasty]

Hawthorn (rose family) is pretty susceptible to various fungal leaf diseases, especially if too wet or too dry, which it is most years at some point!
In a bad year they can completely defoliate. But they should come back OK the next year.
You pretty much have to live with it or spray relentlessly which isn't really practical.

That looks more like a dog rose or similar (rather than ordinary Hawthorn?) with mild leaf (possibly black) spot in the photo.

If you want to spray, Rose Clear Ultra or Systhane Fungus Fighter might help, but affected leaves will still drop/die.

[groucho]

There seems to be many other trees around with the same thing.

[Mr GrimNasty]

I'm afraid it's a fact of life with gardening. It's something different every year - worse/better. My Czar plum completely defoliated with rust last year, fine this year. If a plant is consistently struck down year after year, to the extent it is weakened or aesthetically poor, you just have to conclude it isn't a suitable site, and bin it for something resistant to whatever the problem is.