Hi Croweater,
Welcome to the ABW forum. I have had a look at the Military Campaign Medal and Award Rolls on Ancestry for any links to a Charles Crisp and found a number of C. Crisps', but I'm not convinced that they are the correct person that you are seeking.
Having travelled from Australia to South Africa, I would have imagined that he would have enlisted in a South African Unit rather than an Imperial one, unless you count the one entry that I found for 995 Trooper C. C. Crisp of A Division South African Constabulary. Unfortunately, the medal roll does not give up any further information other than the clasps awarded for the Queens South Africa Medal.
Even though I was unsuccessful in finding any related military service, I was able to locate several news articles for the district of Coolgardie of entries that mentioned a Charles Crisp from Western Australia with links to the Wesleyan Methodist Church in Kunanalling, which is now an abandoned town. See below -
(Coolgardie Miner, WA., Saturday 31 Mar, 1900)
(Herald, Coolgardie, WA., Saturday 31 Mar, 1900)
What is coincidental about the above article, is that it mentions part of the service is talking about the Indian Famine Fund and that you also spoke about your Great Grandfather spending time in India. I was not able to find any other relevant topics after the dates which are shown above.
Trev