Originally Posted by Chris Gilmour

BAEC Gold & Silver members can access the domestic SLOW lounges in JNB, DUR and CPT, provided they are travelling on BA flights internally. They can also access the international SLOW lounge when travelling to regional destinations such as Livingstone, Windhoek and Mauritius on BA flights. These flights are operated by Comair and earn tier points and Avios in the same was as regular BA flights.
A further concession is that BAEC Gold & Silver members can access the domestic SLOW lounges when flying on non-BA flights, provided BA does not fly to the destination on the ticket. So, for example, last year I flew to Bloemfontein on SAA/SA Express but was able to access the SLOW lounge at OR Tambo as BA/Comair does not fly this route.
It should be noted that the SLOW lounges, while owned and operated by Comair, are not for the exclusive use of BAEC cardholders. Indeed, FNB Private Bank and RMB Private Bank cardholders tend to be the main users of the SLOW lounge facility and they can use the lounge regardless of which airline they are using.
The international SLOW lounge is not accessible for premium passengers on BA's international flights out of OR Tambo ie BA56 and BA54.