Been pondering this myself. Not sure how it is on the Stilo, but a mate got some mesh from Halfords, painted it to his liking and bent the edges. It then attached to the hooks which would have held his original mesh/grille in place. He had a Pug 106 though, so as I said, not sure how it would be on the Stilo.
If it's the same as the main front grille, it's those annoying clips that come out with the help of a flat bladed screw driver. They break rather easily though, so I'd be careful. Plus, if it is them, I'm not sure what you'd fix the mesh with unless you got some strong flexible adhesive or something :chin: