Quick wander on here suggests a few hillforts nr St Austell. I have no idea which one this refers to however. I don't have the OS map for the area & gave up after 20 mins on multimap trying to locate the farm in question. Hence why I threw it on here.
That probably answers your second question as well!
I clearly have no idea, I just found the page on the net last night whilst wandering...
:)