You're a star! Thanks for the very quiock response!Hello Jonathan ... the one post would have done unless you have 2 Espaces ...
If the plastic strip is removeable and it revals a metal channel, then your options are Renault roof bars that form a spoiler when closed, similar to the higher spec models, or Thule also do a set of bars (classic or Aero) that fit with the correct kit, they dont slide though, as the Renault bars do, but are flat and have a greater load capacity.
Do a search for Espace and roof bars plenty of info on Espace IV's
Hope it helps