Maureene is absolutely right of course about the surviving WO97 records but I would like to mention that there are, sometimes, exceptions. I only discovered this when researching a fellow whose China 1900 Medal I acquired. 64683 Bomdr. F. Coveney RHA died of hepatitis, in service, at Lucknow on 20 April 1903 but his service record survives in the WO 97 series. He left a young widow, Sabuia Howlett, and this may have led to the papers surviving in case of pension disputes, etc.
I have known a couple of other medal collectors who have had the good fortune to find records of other men who died in service so the message for researchers might be to have a look anyway ... just in case.