How do i fix a broken double glazed window lock?

We have a broken window lock on one of our double glazed windows, the spindle i believe it is called just keeps spinning around so not opening the window. I understand it can possibly be replaced by removing the whole handle fixing, including the insides. The problem we have is that it is locked shut so we cannot get to the insides from the bottom of the window frame. Any ideas how to get the window open without damaging it?