Hi Bronwyn,
Map Studio used to publish a 6-CD pack of the whole country’s 1:50 000 Topo maps and you could select and save the specific maps (in TIF format) that you want to look at. It might be substantially cheaper than buying each sheet (provided they are all still in print), and will give you the whole country in one box”.
I got mine from the Map Office in Jan Smuts Ave, Craighall Park a few years back.