Pretty sure someone on the megane forum found a ball joint off a 1998 scenic was the same one on the megane but which one im not sure and if the same as the clio im not sure either.
You might want to fit some thick washers under the centre shock nut, as kw's used to do this and it turned out the thread on the centre of the shock ended nats cock short of the rubber so the nut wasnt tight up against the rubber. Maybe a cheaper option to try first