This story must have been planned for quite a while (perhaps as long ago as when they popped Rex in a canal boat), so I don't think it can be Roy who is deaded.
I also think that Joy is safe, now that Mick is getting a surname.
It might be one of the elderly actors, or somebody we've not heard of for yonks.
Who would be out and about at 9/10pm? Rev Alan on a mercy mission? Freddie (might solve the inheritance issue)?