If you have an AMEX Plat or Capital One Venture X, allow me to recommend the Virgin Atlantic Clubhouse. Great a la carte menu and bar, plus showers.
I find the SAA lounge quite depressing, though there are showers.
If you have Priority Pass, there are other options as well...all somewhat depressing. Avoid the Mashonzha lounge, as it smells like an ashtray (it has a smoking room with poor ventilation). The Aspire Lounge is better than the Shongololo Lounge.