Legal Advice Sought

Hey Guys
English elderly friends of ours are about to buy a house in a village in Herault. They depend on us for help/advice. The garden backs onto another at a lower level. The owner of that house proposes to heighten the wall for privacy. Our friends do not wish to proceed with the purchase if this happens. They have sought advice from their Notaire who just phoned the selling agents and was told that the neighbour would have to have permission from the would be purchasers to heighten the wall. I am not at all confident in this advice. Is there, for example a length restriction whereby the neighbour could heighten the wall without permission of the purchasers?
Good luck

 

From what I recall from years ago the maximum height was 2 meters, you need to check with local planning