Bakela,
Had the same thing in '87 trying to get back to Phalaborwa from Nelspruit in a C172. Weather socked in and no matter what we tried we could not get over / through the valleys. Ended up back in Nelspruit for a couple of days - luckily we were on leave and not pressured to get back for work.
Its a real ****ty area and it can change so quickly. The mist is really a pea soup and it makes it an absolute sod for visibility.