Boer War 1899 - 1902

I Live in Australia and have been researching my family history. My Grandfather Henry Longstaff was shown as being a soldier in the 1901 Census, he was also in WW1. I think i have found details to obtain his service record for WW1 but not in 1901 which I presume would be the Boer War, How will I find out where he served and his regiment