Xalanga is a village in the Eastern Cape, directly north of East London and close to Cala and Elliot.
The Xalanga Mounred Rifles was service in the Boer War and medals were issued to this unit.
The WO100 index says the XMR roll is at the end of WO100/278 but it is not in the PDF version available from TNA, nor is it in the version available through Ancestry. For the discussion on this, please read the forum post.
If anyone has any information about XMR QSAs, please contact the site owner.