While the Rag area is closed off to the public for safety reasons I'm adding an alternative way to calculate the coordinates, based on the INFORMATION BOARD at its entrance:
The boatmen of Lympstone and Starcross reaped rich harvests in A850 and supplied 20 - B0 tons of mussels every evening to the London markets.
Purification took C8 hours.
The letter L appears D times in the title at the top of the information board.
There are E letters in Powderham's building of historical interest.
There are F letters in the name of the saint to which the church at Powderham is dedicated.
The following original questions can be used once the Rag area itself is made accessible to the public again:
One of the seats here is dedicated to Elizabeth Marion Stowell.
The formula for the cache hide can be calculated using her birth and death dates:
Elizabeth lived from AB.C. 1954 until DE.F. 2004
The cache is hidden at N50 B (F + D). (E - A) E (C - D) W003 (A + D) (A + B + D). E B (C - B)
Please be aware that the headline coordinates area at the seat itself is close to the edge of the estuary so children and dogs need to be watched carefully.