I know rather well this kind of terrain as I had been assigned for 8 years in Western France.
The most common species of deciduous trees are European Beech (
Fagus sylvatica), Pedunculate Oak or Sessile Oak (
Quercus robur or Quercus petraea) , Chesnut (
Castanea sativa) and Hornbeam (
Carpinus betulus). Before it was nearly destroyed by a parasitic fungus in the 70's, Smoothleaf Elm (
Ulmus carpinifolia) was also planted.
In low-, wet-lands, ie near river or marshlands, we cand find Common Alder (
Alnus glutinosa), Common Ash (
Fraxinus excelsior) and various kinds of Willows like the Wisconsin Weeping Willow(
Salix alba).
Of course, the hedges are also composed of various shrubs and shrubby trees : Hazel (
Corylus avellana), Blackthorn (
Prunus spinosa), English Hawthorn or Singleseed Hawthorn(
Crataegus laevigata or Crataegus monogyna), dogwood as the Bloodtwig dogwood (
Cornus sanguinea) and some other species deemed useful for the peasants.
Also be careful with the trees : they don't grow "on their own", but are regularly pruned. The most common type of pruning is the pollard : all the lower branches are cut, and the tree sports a massive, gnarled and knotty "head".
Hope it was helpful, and not too academic