OP - thanks for bring up the subject. I am off to JNB next April with a 12 hour layover also and was wondering what to do. I am just heading to a local hotel to shower and hang out a few hours, proabably a nap, before coming back to check out all the lounges.

One question I have is will there be a check on bag sizes for the carryon bag when OP returns since he is on to a BA flight with smaller overhead bins? I am using miles for First Class TPA - JNB so that might get me 'special privileges' or not.