Well, the reason the Male Medium C didnt go into production right away, was because of the limited traverse it offered with its 6 pounder gun. So it seems apparent that at least a prototype was built. Even then, a good number of them were ordered. But because of the armistice, they were all cancelled, and only some Females got built.
I would absolutely love the pictures you have! I cannot get my hands on that book you mentioned, so if you could scan that page or two for me, I would be incredibly thankful! The Hornet is like the Sports Car of WW1 tanks. While others may be cooler looking, the Hornet was probably the only one that wouldnt be a hell to serve in, hehe.