The strict A to the Q is none: the industry itself made very few Product Investment decisions, thus few chances to get them wrong. The UK State, incarnate as Air Ministry (then MAP/MoS/MoA...) for RAF (and, 1918-1939, RN), and Imperial A/W, BOAC/BSAAC/BEAC, did most of the Requiring, defining and paying.
The Q is itself moot, as implying lost opportunities for hefty sales of novelties not instantly copied. The Q also ignores the inconvenient detail, that BAE has made profits on dramatically hefty sales of Airbus wings and bits of Boeing wings, either after repaying taxpayers' Launch Aid, or without calling on us at all. Every other UK aircraft type that achieved a half-decent sales run was taxpayer-subvented, one way or another. So, of course were F-27, Caravelle, the Embraer and Bombardier ranges. (Let me leave WTO to deal with City, State, Federal taxpayers and Boeing).
The biggest fluffed decison within the competence of industry Boards was to surrender General Aviation. Nothing post-WW2 to follow up the sector from Moths to Anson.
Each candidate "blunder" here posted involved Ministers making decisions under uncertainty: none was done capriciously. So: 9/46 sale (not gift) of Nene and Derwent was to our valiant Ally, with whom we would have to live after the departure from Europe of GIs before US' 1948 Presidential Election. They were bartered for Ukrainian grain, intended to pave the way to a long term, $-sparing means of feeding our people. Uncle Joe in 1948 in Berlin had other ideas.
So: DH (with Fairey and Hunting) getting the 1958 medium haul type wrong was due to listening to the sole funded Customer. Their Boards would not have put up 50%, nor MoS the other 50%, of R&D for a product with no Customer.
The book and this Q dodge a killer Q: Why should taxes prop up Air? If firms see a market Just Do It! and find investors, like all other ideasmen. Bristol, Hawker Siddeley, Rolls Royce, Vickers did so in other sectors. UK Aero's Product Investment risk aversion was not due to blunders, but to blinkers.