Well, it may be that some people believe Summerisle exists and has some true facts.

The story of the writing of the film by Antony Shaffer is told in the book I referred to in my previous post.

All the pagan stuff was based on material found in Fraser's "The Golden Bough". If you believe the Golden Bough then I suppose it could loosely be described as based on true facts.

You can read it here http://www.sacred-texts.com/pag/frazer/ - always supposing you have no paint to watch go dry.