JV is right, you do not specifically need V25 to get your MkIII to the latest update. V22, V22.1, V23, V24, V24.1 and V25 will all take the MkIII to 3-1/63.
There are some links here that can help you obtain one of these version -
http://www.xoutpost.com/articles.php?...ticle&artid=88