At the risk of answering my own question, and just for the record:
In the end I didn't have the need for a NetCafe but saw loads of them in Cape Town - some look more professional than others - if I did have a need in the future I'd use those in the Tourist Offices, or as mentioned above the Library.
I tried the WiFi system at Cape Town Airport (conveniently situated at the gates) but was rejected by their server though it worked perfectly ok at Joburg International Airport. - though this last location was the most expensive I came across.
But then I was too busy sightseeing for netting...
Cheers
amofw