Tch tch, can't have been too many NADA's with that fitment! I had exactly the same problem when I sought to fit these to my Thai car. I didn't resolve it and Lucky will, at some point, get my own version of the system using P5 type above door interior lamps instead of the open type fitted by Rover. I found some really neat little rocker switches as well that are small enough to fit next to them. I shall use a fixed wire rather than the plug in one, as the headrests, once adjusted to your liking, are then effectively fixed.
Chris