The above co-ordinates are not for the cache, they are for the Normandy village hall car park, where you might begin your search. The sundial is not too far from here. Its a short walk (certainly less than half a mile away).
If you were deciding upon a place to put a sundial then a large sunny open space like this would be a good choice.
This sundial however is in a shady spot overhung with trees. A poor location you might think, but this is an invisible sundial which has never had a gnomon.
You must find the sundial. It has a plaque with the dates 19AB-19CD, and fortunately this plaque is visible.
Now a few calculations:
E = Edwards initial (convert it to a number using the usual method)
F = B + C + E - D
G = (C*D) + B - A
H = A + B + C + E
X = (B*C*E) - (D*H)
Y = (F*G) - (A*H)
The cache is at:
N51 15.X
W000 40.Y
You probably won't need it but you can check your answers for this puzzle on GeoChecker.com.
The cache is a small camo container. It doesn't contain a pen so bring your own.
Good luck and have fun. Please do not leave any spoilers in your log.
Note:
I've rated the terrain as 1.5 but the sundial can easily be reached by wheelchair (even on a wet day). The cache is slightly inaccessible which is why I decided upon 1.5.
The sundial isn't on private property and can be found 24/7.
My puzzle cache "On 21st July" (GC1W4MY) contains a hint for this one.