Steve6443: not all MIL areas are active on any given day. In order to check which ones are, the DGAC produces AZBA (Activité des Zones Basse Altitude) charts daily. You can find them on their website here:
https://www.sia.aviation-civile.gouv.fr/default_uk.htm
Also, if you want to double-check in flight, looking up the nearest air base's APP frequency on the half-mil chart and giving them a call works fine.
GA airfields are generally viewed as a local asset in France - that's also why local councils sometimes own them and why there are often no landing fees (running costs being partly shouldered by the local taxpayer...)
That said, GA flying in the Czech Rep looks awesome!
Cheers
