I'll come back and read your fascinating history when I have time to savor it. But I wanted to point out that the Roundhouse was also an early home for psychedelic music in the 60's (Soft Machine, Pink Floyd). Although there don't seem to be many commonalities for the two genres, Daevid Allen (Soft Machine's original bassist) bridges the gap, and not just in the way that this article describes--as the founder of something for punk to react against:

https://www.theguardian.com/music/musicblog/2015/mar/13/daevid-allen-gong-soft-machine-remembered