Afraid I haven't been in any caves near Capetown - Your best bet is probably to take a look here http://www.sec-caving.co.za/p/about-us.html
While there's plenty of limestone around Cape Town I've only heard of smaller caves there, the more famous area is about 400km away where Cango Caves are located, North of Port Elizabeth.
There's also lots of caves near Johannesburg, It's a 30 minute drive to Sterkfontein, a world heritage site because of the archeological finds there and there's quite a few caves nearby.
You can go here https://captnemo.smugmug.com/search#q=Africa+cave&i=0
To see some pics from a MotherLode Grotto trip I led to visit some caves in Botswana and a couple in South Africa. Unfortunately We didn't reach Gcwihaba, though my parents sent me some pictures from a later trip where they visited it https://captnemo.smugmug.com/Places/Bot ... -BVJWCgM/A