" In France some airfields are not fully open on Sundays (French on the radio rather than English) or lunchtimes."
Not true : French civil airfields never close, unlike UK, Germany, Italy ...
Always fully open from SR-30 to SS+30, even when local ATC are not operative: in that case local airspace is downgraded to class 'G' and pilots transmit blind in French or Frenglish. No PPR (except for private strips and for VFR in biggest airports as Orly ...), just turn in, radio and land ....
Civil French airfields are only closed when waterlogged, works in progress .....etc : see possible Notam.
During lunchtime (noon to 2pm LT) flying is not banned, local flyingclubs are usually closed, avgas delivery too, but not airfield restaurants ....
The poster is NEW to France (other than le Touqet) , so I was suggesting they CHECK and take care. Not fully open - having to make radio calls in French is proberbly not what he wants to do. No fuel available and no customs.