I hate to say this but it needs a remake. (some spoilers)

The idea is sound.
The location atmospheric, the photography very good.
The 'owl man' and the some of the effects make up were very good too.
The soundtrack was slick if sometimes misused.

Sadly the acting and some of the editing lets this film down. I know that the actors weren't very experienced and there is nothing wrong with that but perhaps the scenes where they have to deliver dialogue should have been handled by a stage director as they feel very clunky. Lawrie has flare when it comes to establishing atmosphere and the nightmarish imagery is really great but the a lot of the exposition scenes felt like padding.
We could have lost at least one Eve dance and still got the general idea and James didn't need the tape recorder.
9 times out of 10 he was merely reporting something we just saw seconds ago.
There was a missed opportunity when he was complimenting Eve's intelligence (he could have called her "a wise old thing" ;-D).
I would have had Eve hatch from the buried skull as an owl but have her tell him she was going to fly to Paris (the animal talking scenes in The Last Temptation of Christ would be my touchstone there).

Also what makes films like The Wicker Man work is that the olde gods are misrepresented by established religion. I would have had the owlman frightening to Jamie but once he became his 'companion' learn that he is actually rather sweet.
People are terrified of death but to some he comes as a friend and I would have that with Moloch. The ritual is horrific but the outcome might be a magical outcome of benefit to Jamie's soul. I certainly wouldn't mind living in that house forever.

If someone were to rework the film into something more akin to the BBC Ghost Stories for Christmas it would be a hugh success. Indeed if I were an executive of BBC Scotland I would approach Lawrie Brewster with a proposal to rework the film with perhaps some more established acting talent.

BTW has anyone else had problems accessing the extras on the film disc? I can play the film but the deleted scenes and shorts just go in a loop.