Alex Henshaw .Spitfire demostration film
You may like to try this unusual source in your quest for Alex Henshaws Spitfire demonstration , IWM "Ferry Pilot" WW2 documentary directed by Pat Jackson.
The documentary is about the valuable work of the ATA during WW2 but is also notable for some excellent Spitfire film and may just provide the detail that you have been searching for.
Having read "Sigh for a Merlin " I am looking forwards to viewing this film myself.