Re: make them ALL available AFTER broadcast as well - FOREVER
The BBC TV "Timewatch" series had an interesting documentary several years ago called "Time Flies". It was a location reunion of some of the staff and actors for Peter Brooks's 1963 "Lord of the Flies" film some 40 years afterwards.
AFAIK it has only been shown the once. New DVD releases of the 1963 film have apparently tried to licence the documentary as an "extra" with the support of its original makers - but the BBC price was too high. So presumably it just sits in the BBC archives.