Cynthia, I'm not sure any moving pictures of actual dogfights exist.
The film technology of the time, if I've got this correct, involved
large, heavy hand cranked cameras. If such a camera were mounted in
an airplane, there would be no room for a gunner.

I agree. moving photography from the period, I imagine, would be very rare
indeed.
Also Britain wasn't very good at propaganda films so the reality actual
combat as movie images didn't really come into being until well into WWII.

The only places I could think of that might be able to help would be the RAF
or the Army Air corps. as it was known then. Though who to approach I
couldn't say. Have you tried any of the military news groups? You could try
Pathe news http://www.britishpathe.com though it might be a bit early even
for them... or perhaps the ministry of defence.

Also...how about Germany? they were big film makers and much more aware of
the value of propganda than we were at the time. Again where to start is
anyone's guess...

good luck

Gail