Hi Sue
VB records were not kept. But he may have volunteered for South Africa in 1899. VBs formed Volunteer companies in the Regular battalions and were given new numbers. His record may be on Findmypast, and should refer to his earlier VB service. In the medal rolls (on Ancestry) Volunteer companies were often reported separately. Unfortunately they only give initials, not full forenames.
Militia records have a good survival rate on Findmypast.
If you have the original you should try and do a high res scan of the belt, collar and helmet.
Ken