I agree that it's a nice shot, but I can't really see any grain in such a small image. If you'd like to post a 100% crop, it would be much easier to see.

Superia X-tra 400 is not the finest grain film you can get, although I do like it. Kodak UC400 is probably finer at 400 ISO, but a shot like this was obviously done on a tripod, so you might as well have used 100 ISO film for even smaller grain. I would recommend Fuji Reala 100.

Also, it's possible that the lab over sharpened the image, which could make the grain look worse. If you get it scanned again, you might want to tell them not to sharpen it. Then you can sharpen it as you see fit.

Paul