The FIBIS Fibiwiki page British Army, section Records sets out a wide range of records available, including online records
http://wiki.fibis.org/index.php/British_Army#RecordsIt would be expected that all his Army service records would be found in the same file, if that file has survived. All the surviving WW1 service records are to be found on findmypast or Ancestry.
If his WW1 service file has not survived, you are unlikely to be able to find out about service during the Boer War.
If his service records haven't survived, soldiers wills, or soldiers effects records, the latter available on Ancestry, may be sources of information. There are details on the Fibiwik page.
Cheers
Maureen