Sorry but Labneh is NOT the same same as buttermilk... Labneh is a type of strained yogurt...... buttermilk is the the milky substance usually left after beating cream to butter or as in most cases these days is massed produced my adding "Streptococcus Lactis" to milk..
but back to the question at hand...I have seen it some times in Mega mart but that's about it.....although I would have thought Carrefour would stock it but obliviously not.....