Robin Hardy did a storyboard of the first movie, 280 pages by some accounts, and is planning on making a graphic novel out of it. He talks about that at the end of the (2012) article below. I’ll research this some more but does anyone know anything more about this? I’m especially interested in any missing scenes. (Ingrid Pitt chasing Howie when he discovers her while searching the houses for one…)

Here's a screencap of an article from Sight & Sound (October, 2013) that shows a few pics.

Robin hardy's drawings

More info here (Internet Archive page of 2012, Craveonline interview with Robin Hardy) . Also at the end of this (WIkipedia)