Here in Edinburgh, maybe two or three. Surprising actually, I thought they were supposed to be rare.
The one that stayed around the car park outside has the typical vest that hooded crows possess, except a much darker grey. Last I saw it was February.
The one that feeds near college has only patches of the vest, but in a very bright, light grey. Again, last sighting was early on, March.
I saw one while out on a walk too. I was amazed at how close I could get to it. It didn't seem afraid of me at all.

(this is the one I'm unsure about, because it had the whole vest and only patches of it were a darker grey, the rest was light). That was more recently, probably about April.
What about you, where and when? I'm curious.