One thing which would be very valuable: If you could conduct laser measurements in Mediterranean parts of France. I think we haven't yet ANY laser measurements of Mediterranean tree species. Unfortunately, I cannot help, where to go to measure. I recall beautiful Quercus ilex forest in Port-Cros National Park, but I cannot say if the trees are record tall. In the time, I was there, I was not interested in height measuring.
Jukka Lehtonen from Finnish Forest Research Institute showed me the Finnish record trees which I have registered in the Monumentaltrees. (I am native to Finland but now live in Germany.) He had measured them with Vertex (tangent method) in the 1990's and now I measured them with Nikon Laser. See my report here:
http://www.ents-bbs.org/viewtopic.php?f=45&t=3272
Some of the tall German trees I have found by chance (the 54-m spruce, the 44-m beech, the tallest linden, the black poplar) but many are well known trees or locations I have found from books and Internet. As heights in books and Internet are almost never laser measurements, this is the method I also recommend to you, at least to start with: Search books and Internet lists for possible record trees and go to measure them. There should be very tall oaks and beeches in Forêt de Bonsecours, Forêt de Lyon, Forêt de Bercé and Forêt de Reno-Valdieu, for example. You know probably much better than I.
Deciduous forests are best to measure when trees are not in leaf, otherwise particularly beech tops are very difficult to see.