I've been reading up quite a bit on how standing while working at your desk is healthier for you, so I'd like to get a standing PC desk.
Any ideas where I can get one in or around Cape Town?
Sound like a load of crap. Rather get yourself a good chair at the correct hight in relation to your desk, check your monitor height and posture as well.
entia non sunt multiplicanda praeter necessitatem
Yeah, I'd much rather get myself an ergonomic chair. Standing sounds a bit overkill.
There's nothing wrong with sitting on your arse. Evolution has given you a nice pair of buttocks to sit on. Just make sure you don't sit on your arse the whole day. Get some exercise.
Regarding the standing up notion ... you'll bugger up your knees by standing ... long before you will suffer because you're sitting.