upvc window locked?

My bathroom window has locked shut somehow...! I have the key and upon opening it the handle still will not turn..? Wife says it was pulled shut and closed with the key lock opening up instead of across..! How can I open it as I cant get handle off due to handle not turning so cant unscrew bottom screw. She also said the last few weeks it was chaffing as she opened and shut window, has it moved also somehow..? Im off-shore so not privvy to all this happening