This has been on my bucket list of buildings to climb up in Paris, and finally made it. It hasn't always been easy to access. Just be aware that there are no toilets working in the park and the toilet opposite is shut. It is 300 steps and the views are wonderful. You do all 300 steps down in one hit, so you need to be reasonably fit.
I loved the gargoyles and the views from the top. The gargoyles reminded me of when I went up Notre Came pre fire. Definitely worth doing. Apparently there was an English tour at 2 which I wasn't aware of. I thought the tours were all in French. I did get the gist of it though and there were only 3 of us so nice to do it in a small group.