I'm sure this has been discussed before, many times, but my 2cents;
The standard of training varies a lot. Some instructors are ex-military with combat experience (although not in the R22!), some are spotty teenagers with low hours. Depending on your own personality you might well find that you learn better from the teenager - it takes all sorts and i've heard a few students complain that the ex-mil types are rude, insensitive etc. If you're coming from the UK remember it's winter over here now - and Jo'burg is at 5000ft.... it can get pretty cold! If you like warm weather or weigh over 100kgs you might be better off in Durban. If money is the deciding factor I would wait until after the world cup when I expect the rand will weaken quite a bit & make it cheaper.