My only criticism would be the choice of instructors, as I think getting an RAF Spit QFI (ie F/L Charlie Brown) to do the training would have been a bit more realistic in doing it the "RAF" way, although as they were using Carolyn Grace's Spit I can understand why they did it as they did.
I would have to disagree here. Carolyn Grace is one of the finest Spitfire display pilots in the world. I have a great deal of respect & admiration for what she has achieved & certainly wouldn't object to having her as my instructor.
I did think the doco could give some people the mistaken impression that 2-seater Spitfires were used for training RAF BoB pilots. According to Geoffrey Wellum's "First Light" he had an advanced training course on the Harvard before joining his squadron. His instructor was an experienced old-timer with the rank of Sergeant Pilot.
Wellum was a regular officer & had joined the RAF just before WWII started. Things were different later on when I understand that many new pilots went straight from a Tiger Moth or Maggie on to a single seat Spitfire or Hurricane when they joined an operational squadron. This was also mentioned by some of the ex-BoB pilots in the programme. I'm not sure where the 9 hours training they based the series on comes into it.