The author is in fact Mark Billingham assisted by the TV performer Peter Cocks and this is the first in a trilogy. It has a sort of made for TV drama feel about it.
The eponymous title is both an ancient village with closely guarded secrets and long dark memories and a Celtic symbol carved on the chalk downland. Present day twins on a visit to their grandma become enmeshed in dangerous and sinister events for which they are unprepared, but which destiny mapped out for them centuries ago.
Archaeology, ancient lore, mysticism, TV sensationalism, twin-ship all combine in an expertly paced, tight plot that should attract experienced fantasy/adventure teen readers. I’m not sure it breaks much new ground but the rest of the trilogy might prove me wrong.