This is the Bonus Cache for the Protecting Nature Adventure Lab. There is nothing at the posted coordinates apart from a silage field, and you must complete the Adventure Lab to get the information required to reveal where the cache actually is. You need to walk the Adventure Lab route in order to find the letters A to E. The information needed for the answers is visible on the AdLab pages even if the question doesn't unlock, just in case you have poor 4G signal. Once you have A to E, use the following formula to get the coordinates of the Bonus cache:
N51 46. C C D W002 48. (A-B) E (C/2).
Have fun, and please let me know in your logs if you spot any nice plants, animals or fungi.
I have written a PDF guide to the Dingestow Butterfly cache Series that might be useful for people working out which puzzles to prioritise. I promise it doesn't contain any Hints though.
https://drive.google.com/file/d/1eCgwQKhpjCcAXxTjjhAUnEFyospeDkON/view?usp=sharing