You were looking at the 8703 OS.
Yours is a 8700. You want this one. http://www.blackberryforums.com/gene...le-europe.html
Follow the instructions specifically as written. Backup your BB first, and sync too. Read the thread--some users DON'T like the 4.2 OS for the 8700, some do. You will need to decide for yourself if you want it for that one feather of separated SMS messages.