>I bet there are long-forgotten stones still hidden in undergrowth or gorse
Withoutadoubt.
That's what's needed Nigel, someone needs to come up with a nice tight Popperian experimental design, one that sets out to disprove. Any finding contrary to disproof could indicate there's something in it.
Badly paraphrasing JBD Haldane: "There are no subjects too unscientific for study, there are only unscientific ways of studying subjects."