The rail you have is similar to the one in my westy, i just have threaded the curtain through, as already mentioned above, and it's the same on the side and back window. Though, where you have the curved edging around the sliding door track, i have a curved rail with Silentgliss runners fitted to the curtain like this:
Though mine has these poppers fitted, to which a curtain can be clipped on around the front window. I also also some rails above the front doors, I just tend to peg my large curtain around the sink vent pipe and sun visors as i haven't got around to fitted the poppers i need onto my curtain - yet another job to do. My curtain is one piece not 3 so i cant have a small curtain on the doors.
so they would be two for each side window because of the join in the track,not as one how some people sale them.
so for the slider i need somthing like alistair.