Owning your own home

Don't want to fix the window and then not have ventilation. And if i stick with that window, it isn't even going to open properly. Might have to ditch the window it and fit a normal sash, which can be opened when I shower.

If you ditch that stained glass window, I will find you and kill you. And you'll need planning and consent to do so in a CA.

Windows are terrible for ventilation in bathrooms because they don't provide what you need - an incentive for the wet air inside to exit the building. They can let wet, cold air in that furthers condensation and damp. They can push the wet air in the bathroom in to the rest of the building.

Doing a hole in the wall isn't really possible if I move the shower where I was planning to, because that wall is shared with next door. It could be at the other end of the bathroom though.

Yep extractors should be in the farthest point from the entrance so they pull air across the entire surface of the bathroom. Because of the layout of your bathroom this is tricky. Directly above the shower might be good enough but it might limit your choices because it's a wet area. You can use some ducting in the ceiling to route it to an outside wall on the assumption you are allowed to do so then make an exit for it. Like they did with that bastard boiler flue.

A good dehumidifier will work wonders however, better than relying on a window.