I guess you could do some kind of language accept detection and serve a "sorry" page. But that would be far from effective or ideal.
If it were me, I would not do a negative "we don't" notice, but some kind of positive "serving x, y, z, areas" banner. And maybe in the meta description too.
The site might still come up in search results for those you don't do business with, but they (hopefully) will learn that fact early on. And having the names of places where you do business may even help for those searching that are in those areas you want to do business with.
I wouldn't go overboard listing every village and hamlet, but some of the larger regions should do.