How do you get to the window mechanism of a rear door of a peugeot 407?

When trying to close, my rear electric passenger side window is sticking near the top, and then automatically winding itself down again, so that I can not close it properly. When operated it grinds a bit and then stops completely and then winds down again, as if it has caught on something that has activated the child safety mechanism. I am unable to work out how to remove the inner door pannels so that I can check the window mechanism for the obstruction. Does anyone know the secret of removing the inner door pannels?