Ok, cut a small length of timber longer than the hole is vertically, screw a screw into it put the timber through the hole and place vertically so that the ends of the timber are now behind the plasterboard by enough distance to then screw through the plasterboard and into the timber. (Get me so far?) then you can screw a new piece of plasterboard onto this newly formed batten and the one that is 50mm away (which you will have to cut the hole out to)
Hope you understand that, i`m crap at explaining things like that
Turkish
