Cache is not at co-ordinates given.They are for the middle of a free National Trust car park.
At N51'15.785 W000'18.869 is a notice board which holds the vital clues for the first two caches of the series.
This cache is at:
N51°15. PQR
W000°18.XYZ
where P is the last number of Charity
Q is the number of letters in the Gallops place
R is the number of letters in the fourth word under Welcome
X is the number of letters in the place with the Heath
Y is the number of letters in the word before Hill Fort
Z is the number of towers minus the number of forts
Inside the inner lids or at the bottom of the inner containers of the first four caches are the clues you need to combine to give you the hint for the fifth cache.
You can check your answers for this puzzle on GeoChecker.com.