how do I replace the battery in a 2003 clio key fob?

I have read all posts on this subject but none are applicable to my model a 1.2 2003 clio.the key is offset in the fob and 'top half' of fob has a 'bulbous bit' that I can pull up at the end nearest key but doesn't seem to come off and I dont want to break it!(this side off fob also has a small light in it)can anyone help please ?