With respect to Boogie87 I would not recommend taking special leave without letting your employers know what it is for! If they allowed you this, thinking it was for some kind of medical or emotional problem and then found out it was due to elective plastic surgery, then you could be in trouble with your employers! If one of my employees did this to me, the first thing I would do would be to contact my employment advisors to find out if I could bring disciplinary action against my employee! My suggestion is as per pickles answer and ask your employers what they can do for you. If you need this surgery for emotional reasons as well as purely cosmetic, they may take a sympathetic view and allow you to take some of the time as official sick leave.
Best of luck, Sue.