I've asked such questions with good response and success on the Society of the Military Horse forum.
http://www.militaryhorse.org/
Try also a Google image search "saddles, bridle+1900+British army officer" but you'll have to be selective.
Finally wouldn't a British officer of the period be expected to provide his own horse and "furniture" as opposed to using British army equipment? If that's the case, there would be much less uniformity in selection, probably a lot more sports and Fox and Hounds related saddles and equipment would be used, wouldn't they?
Good luck!
All the best,
Dan