I have posted many a time on here when someone at our place has ran a cryptolocker.
When we've had cryptolockers since I've been there all but 1 of them has been stopped from spreading through directories by user permission access, I think that was odin or it might have been zepto I can't remember there's been too many.
I'm not surprised this has happened, what I am surprised by is that it is spreading across multiple sites (?), I've no idea how NHS sites and file shares are linked, unless lots of people have been duped by the same email today?