<i>if there was any difinitive way of finding out such things</i>
Well, you could send him an old wire coathanger cut into 2 equal lengths, both bent into an L-shape and a link to Sig Lonegren's dowsing instructions.
See what he finds!
http://www.isleofavalon.co.uk/GlastonburyArchive/sig/spirdowsing0.html
"Ways of seeing
It is important to remember that not all Earth Energy dowsers 'see' these energies in the same way. Since Spiritual Dowsing was first published in 1986, dowsers Hamish Miller and Paul Broadhurst have dowsed the 'Michael Line' – a geomantic corridor discussed later in this book, running from St Michael's Mount in Cornwall to the Northeast through many important sites including Glastonbury Tor and Avebury. Instead of the energy being straight as with the energy leys discussed here, they found two curving lines (called the Michael and Mary lines), like the serpents on Hermes' caduceus, crossing at the major points of power along the way. It's OK to 'see' it differently."
Rune :-)