The sort of things I'm wondering include:
Is it possible to tell whether it's the Boer War, WWI, post WWI, or one of the other conflicts around that time period?
Is it possible to tell whether he's cavalry, artillery (driver), mounted infantry, or yeomanry ( I believe, possibly incorrectly, that the yeomanry was the mounted arm of the volunteer force, which became the TA)?
Did the different branches of cavalry, e.g. hussars, lancers, etc, have any distinguishable features in their field uniforms and/or equipment ?
As an aside: Is there any way to confirm that a soldier photographed on foot is from one of the mounted branches.
I know that cap badges are a very good way to identify the regiment to which a soldier belongs, but many regiments have similar cap badges. E.g for this chap I've found around half a dozen mounted regiments whose cap badge could match that in the photo, ignoring the many infantry regiments that match because, well... the chap's sitting on a horse.