Probably nothing of note.Something I've been thinking about: did the British aero industry lose some supplies of manufactured parts or raw materials from France when it was lost?
It was the French aero industry that struggled to deliver important parts of aircraft, so we have the often-mentioned case of aircraft delivered without propellers. France was eager to import much greater % of the aircraft from the US than the UK. British aero industry out-produced German counterpart when it was about the raw number of aircraft by some 50% in 1940; unfortunately, in 1940 the British aero industry delivered a lot of aircraft that were badly behind the curve, so the effect of that output was smaller than it should've been.
In 1941, UK was out-producing Germany by some 70%, and already in 1939 they were almost matching the German production, despite the German earlier re-armament. French were eager to have Merlins installed on many of their aircraft, and were on the top place to receive Spitfires once there was enough of them for the British needs.
This also kills the argument that British aero engines were hand-produced - a thing that our friends across the pond have hard time digesting for the last 75-80 years