I found a decently priced fare from LHR to CPT with a stopover in JNB on Virgin Atlantic. In JNB, I would have to change planes to SAA. The stopover is 2 hours. I'm assuming I will have to go through customs in JNB. Do you think 2 hours is enough time? Or should I just book a later connecting flight from JNB to CPT on Kulula or Mango?