Good news! The Anglo-Allied Army is indeed adequately represented! Here is another photo, identical to the one above, showing the figures dealt out to each base.
After lots of snipping figures off sprues, I now have enough for each base. Looking at them all in one go, some things stand out. Specifically, the variation in Quality! Revell are good but a touch thin and elongated; Airfix are strangely mis-shapen; Mars appear to not use plastic at all, but rather some strange substance closer to old chewing-gum than anything else; HaT are good and generally more 'uniform' in pose than anything else. The two stand-out facts are a) Italeri are easily the best quality, and b) there really is no excuse these days to not mould a horse and its base as a single unit (you hear that Airfix, Mars and Esci? We all hate trying to fix some horse's leg into a tiny slot!)
Next up, the job of slowly glueing each set of figures to a strip of cardboard!