sole joy here is to tell you the trio of why something wouldn't, couldn't or shouldn't have occurred.
Like reality
Of course we must not ignore reality and the technological limitations of the time
Reality being physics ( lift/drag ) actual power at altitude, available fuel at the time in question, available factory space and/or design staff.
and dozens of other trifling details, like
bolt some expansion onto it's the Hurricane.
Reality rears it's head in the form of center of gravity. You don't just bolt 4 feet of extra fuselage into an airplane behind the existing center of gravity.
Why was the Skua's nose so long? they screwed up the calculations for the center of gravity and had to move the engine forward by a considerable amount to get the airplane to fly right.
Gravity is one hell of a contrarian.
BTW the book "Hawker Aircraft since 1920" by Francis K. Mason has a few details that seem either at odds with the above sources or raise more questions.
Commonly quote range is 940 miles, while clean. However the fuel capacity is listed as 94 gallons. We either have a misprint in either range or fuel capacity or the Henley was most economical aircraft of it's size and power ever built by anybody. No mention in the text about a bomb bay fuel tank.
Strange coincidence, the Henley, while using a whole new wing center section compared to the Hurricane and thus 7ft 10 in more wing span had exactly the same wing area as the Fulmar.
342 sq ft.
First Henley used fabric covered wings. 2nd got metal covered ones.
Henley's speed advantage over the Fairey P.4/34 bomber (Fulmar parent) may have come, in part, due to a bit marginal radiator setup?
It was a chronic over heater in target tug duties with many more problems than the Defiants used as target tugs.
Book also claims that Henley's career ended in 1942 with under 40 aircraft on charge in June of 1940. Be careful of wording as the claim that "remained in service" could refer to as little as 1-3 aircraft?
The Henley production line at Glosters was shut down in mid 1940 and the space devoted to increased Hurricane production.