Hitler's Blitz through Poland was much more primitive than what he launched at W-Europe. One of the main attacking aircraft was a Bipe (Henchel), and the army was largely horse-drawn. The firebombing on Warshaw was done with JU-52's where they shovelled incendiaries out the cargo doors.
My point is, that both parties came a long way before 1940, not just the British.
FYI, Spitfires claimed the first LW victim in 1939, over Edinburgh. Was a bit of a shock to the Germans....