Two books published in 2008 in England are the best biographical sources I found so far:
The Letters of Noel Coward – Google Books
Noel Coward In His Own Words – Google Books
This is the 42nd post in two years about astro profiles in the BofL Lessons. This is less than a quarter of the total but includes the ones most relevant to readers today, still famous enough that books and videos about them are readily available online. Nine more are ahead in 2025.