is possible but sometimes requires you to adapt bits to make it fit, as long as its not pre and post facelift.
Just a quick note, have you checked with your insurance what they will charge you once you fit the cooper s bonnet? make it look like a cooper s and the chances of it getting stolen increase as will your insurance, just check that out first!
I am adding a cooper s spoiler to my mini one and my insurance is going up buy £29 per month!!