This particular documentary - That Was Then... This Is Now - is up there with the rarest and was recorded in 1988 (that's 22 years ago, feel old?) by my older bro. I've finally got round to digitising the VHS (thanks gZa) so i can watch it on DVD and also uploaded it to YouTube this morning. See below:
I don't have a huge amount of information about this other than that it was part of a series of six 30 minute rock documentaries made in 1988, directed by David G. Croft. The others included the Pet Shop Boys, Spandau Ballet, Gary Glitter, Depeche Mode and John Lydon (aka Johnny Rotten) .
There's also an executive producer credit for the infamous Janet Street Porter.
You can't buy this documentary anywhere as far as i can tell (if you could I'd point you to that rather than posting on YouTube). I can't imagine it'll be appearing on DVD anytime soon either, I'll leave you to figure out The Reasons Why.
The Cure - 4:13 Dream album review