The simplest "lay explanation" answer is that a wing does
*not* create a circular flow around itself, at least not in
exactly the same sense as the spinning ball. The air
molecules approach the wing, and flow over either the top
or the bottom. No air molecules ever actually go over the
trailing edge and forward along the underside of the wing
and then back up over the leading edge. The closest thing
to this is: Since air pressure is quite low on top of the
wing, and high below the wing, some air molecules will be
sucked from near the front bottom of the wing and up over
the top (that's what triggers the stall warning vane).
However, air never really spins completely around the wing.

OK, that last bit makes sense to me.

The gap in understanding is now exactly *why* air pressure is lower and
speed is faster above the wing. I accept that air that goes over the top of
a positive angle of attack wing with a positive angle of attack is sped up
and, and can grasp how this creates pressure differences that results in
lift.

At first I tried to explain it to myself that the air isn't actually sped up
above, that what has happened is that air below is slowed down due to an
obstacle effect so the air above is just faster in relation to the air
below, but this can't be right because the pressure patterns of a wing
generating lift show a decreased pressure in relation to ambient pressure
rather than just an increased pressure below.

So I arrive at my current quandry. What influences the air molecules that do
go above the wing to speed up? What forces are acting on it? Is it a case of
"speeding up first, reducing pressure, therefore pulling air over the front
of the wing above the stagnation line" or "reduced pressure, increasing
speed of the air above the stagnation line"?

I'm sure this all seems so ridiculously easy to those of you who understand
it, but there's just a lightbulb that hasn't gone off in my head yet.

Thanks in advance.