Just a Guess...
Are these possibly two locations, e.g. a flight from the first location to the second?
If this relates to the 218 squadron, whose final base in France in May 1940 was at Nantes Château Bougon then maybe the two locations are on the French Lambert Zone 1 or 2 maps , vX236100 and vY291600? or wX, wY on the zone 2 map.
see
http://www.echodelta.net/mbs/eng-welcome.php