Going to have a tough choice in Midrand. Only White lady in Midrand I think is
www.esa.co.za/escorts/viewEscort.php and doesn't offer FH (I don't know if she is multiracial).
Maybe check Pablos:
www.esa.co.za/escorts/viewEscort.php (not open on Mondays I think).
Might have to expand your search to Centurion or Sandton.
I used to see a White lady now in Centurion who was multiracial (I'm Indian, I cannot confirm if she caters to Black gents) but I don't see her ad up at the moment.