If you mean the Maisy Grandcamp battery, its at GPS 6402 54707 and GPS 6407 534710 and can be easily found using the French IGN 1:25,000 Maps, Sheet 1412OT.
I was given the following directions. Maisy is 1km SW of the harbour at Grancamp-Maisy. If you follow the D 514 South from Maisy, and turn Right (West) 300 metres after leaving the village on to a minor, unclassified road that runs SW along a spur. There are two sets of casemates very close to this road, the first group on the left and the second 700 metres further on, on the right. This minor road is the only way to approach the position.
To say that they have been "discovered" is a little innacurate. I think they have always been there on the map. The important step is that someone has bothered to obtain access, tidy them up and open them to the public and good news for anyone who is interested.