I had a quick look through "Stirling" and "Honours and Awards" and I could see no reference to the 3rd Bn., The East Kents. However, the SAFF Casualty lists show returns from June 1900 to April 1902 for the 3rd Bn., East Kents. There are far too many individual entry locations for me to record here - some forty and they seem to have had a high proportion of deaths from disease. Some passed away on St.Helena.
Perhaps the 3rd Bn., the Buffs were used as reinforcements for their 2nd Bn., they don't appear to have been listed for the Mounted Infantry.
Should you manage to get a copy of the SAFF Casualty Lists, you might see the locations of casualties and the like - and thus obtain a picture of their activities.
Good Luck with your quest