Are you aligned with Marriott Bonvoy at all?
https://www.marriott.com/en-us/hotels/jnbor-protea-hotel-or-tambo-airport/overview/
I've stayed at this place a few times and it's not far from the airport. I really like its Av/Industrial style theme.
I spent 4 hours there and felt like I needed more. To help balance out what I knew from history and had also spoken of at length with my Afrikaner friend's. Who having grown up through Apartheid had their own opinions. Well worth the visit :cool:
Cemair is another one that is basic but decent. Although they mainly have the dreaded Dash 8s. I once flew JNB-DUR with lounge access for AUD$100 which included a beer and a packet of crisps on the flight.