Most people who use temperature controlled mash rigs are only heating. I can't imagine that anyone is trying to cool his mash tun.
I'm not sure what you mean by "dialing in" the boil. Water boils at 100ºC, and it can't get any hotter than that. If you turn your element on, it will heat the water until it starts to boil. You can adjust the power manually to get as gentle or as vigorous of a boil as you'd like.
The generally preferred tool for this is a PID with a solid state relay. In the States, Auber is popular, but I'm not sure what is easily available in South Africa. Do your research, though. You don't want to electrocute yourself with bad wiring!