Hooray! Found it at lunch time today, after an unsuccessful attempt last night. Thanks to Andy for fixing the clues so that we could try again!
Today was a lovely bright and sunny day to come back. After finding the cache, we sat and ate our lunch, admiring again the adorable puffball ducklets and watching the huge (huge! holy carp!) fish float lazily through the water.
Took two smelly tea lights and left a screaming monster key ring.
Thanks for the hunt in a nice, peaceful location!