Re: Performers from original London cast, no longer with us!
I think that apart from those you've listed, all the original cast members are still alive and kicking. I don't know about orchestra. As for creative team, Maria Bjørnson, set and costume designer, passed away in 2002. A great loss.
I wish I had some answer to give on David De Van... but no. Instead I have a photo:
"David De Van, in his understudy costume for Monsieur André. Sadly David passed away not long after these photographs were taken."
(page 44-47 in Marcus Tylor's "Phantom, the first year backstage 1986-1987)