It looks like 'The Delian Mode' will make for a really interesting 25 minutes; Delia was such an interesting and influential person and her music still sounds like the future, over 40 years after it was made -- quite a feat. Calling her a visionary wouldn't be too much praise.
From the trailer it looks like the documentary is more about the images Delia's music provoke than her as a person, but I hope there's some mention of her life or career. She worked as one of the few women in that field and in the 1970s she just stopped composing. She only started working on music again in the late 90s, shortly before her death in 2001. Why did she give up on something she was so good at? That always fascinates me.
You can see the great BBC Four documentery 'Alchemists of Sound' (about the BBC Radiophonic Workshop) on YouTube.