The bug/blob grills are completely different shapes so the parts are not interchangeable i'm afraid.
You will need to drill 3 small pin holes in the bumper to fit, otherwise there's nothing to hold the base of the grill in place and it will just flap about. You'll also need to screw into the black plastic shroud at the top to hold it in place, although the two centre screws are hidden behind the number plate. A bit of black paint on the outer screws and they disappear from sight unless you look really closely.
If your front plate is stuck on, worth changing to screw fixings so it can be removed easily without having to re-do the number plate tape! (You'll want to remove the grill fairly often to clean behind it!)
Whilst it seems nuts drilling the bumper, they're tiny holes and not really noticeable. Worth it for the look:
