The suggested Parking co-ordinates will get you close to the park entrance.
Once at the listed co-ordinates you should be at a plaque at the entrance to the "Enchanted Wood".
Find the first number on the plaque, only using the last two digits subtract 7 and this will become AB
Mark your position at the plaque with your GPS. We know that there is a "Magic Cave" on the opposite side of the "Enchanted Wood" to the plaque.
Your job is to take the GPS, find this cave and walk through to the other side.
Once you get to the wall on the other side stop and check your gps, ensure you have a good fix.
* If the distance to the plaque is more than 35 metres then CD will be AB minus 29.
* If the distance is less than 35 meters then CD will be AB plus 29
You must now find your way to "Treasure Island", there are a lot of ways, most will take you past many distractions, once past these you will need to get around the stone guards standing at attention and the cache will be yours.
The 400ml cache is located at:-
S37.16.8AB.
E142.55.7CD.
BEWARE OF MUGGLES WHEN ON TREASURE ISLAND
Good Luck and Have Fun.