So, Jon has a strong accent. Actual English people would recognize it as Yorkshire but would probably recognize the city, Sheffield, too. There might be some social stigma related to that in Victorian London -- the parts of Yorkshire that aren't farms or moors tended to be industrial, often nouveau riche, etc.

Would people in this city recognize it as "from up north somewhere" (even if they mean "an island to the north") or would they be unlikely to comment on it?

Asking for a friend, a friend who incidentally finds Gef the Talking Mongoose both utterly terrifying and kinda delightful.