There is also an argument to be made that much of the progression and success were seemingly deliberately lost in the inter-war period, especially with regards to the use of tanks.
Not sure whether I agree that it was intentionally deliberate, but you're correct that swathes of our technical and tactical advancements were lost.
It wasn't immediate of course as in the early to mid 20s we were still at the forefront of tank design and doctrine, and the RAF thrived in Iraq.
Our demise only really started to take shape in the late 20s to early 30s when cuts, squabbling and pressure from more rigid ranks pissed it away.
Tanks were too small in number and were primarily light tanks, designed to police empire rather than oppose a foe, and supported the infantry.
Germany on the other hand saw the infantry's role as to support the tanks who'd move on mass and in speed; as we all know it didn't end well.
Additionally, France had some of the best tank designs in the world in 1939 (much heavier than their German foe) but used them in isolation.
Much could be said about the RAF as well and losing their advantage through squabbling, poor procurement and back to outdated tactics.
On paper we and the French should have given the German's a stern fight in 1940, but as you said we'd lost all the progression and sank back.
Same assumptions, same poorly thought out doctrine and the same ol' mistakes. Like in WWI, took a good few years to iron them all back out.