Yes, I would move there straight away IF:
I could find a job to support myself and my family . IT, engineering and education are needed.
And enough money to buy a high-security property with alarm and armed response
Afford a good medical aid plan, healthcare is world class in private hospitals, but at a price.
Find decent schooling for my children - private schooling is expensive
afford enough insurance to cover theft of car, household etc
the government would severely penalise rapists and do everything to reduce the spread of HIV-AIDS
the country had a reliable police force and a justice system
corruption was eliminated
Above all, remember, your experience in South Africa as a holiday maker with pounds to spend, will definitely not be the same as someone living there earning rands.
UK is for softies, really. South Africa is for real. Don´t expect the state, the police, the social security system to help you out. not even if you were black.
Cape Town is great, also my first choice of cities in South Africa, especially if you like the laid-back style. Johannesburg is fast pace, pure city.
Cape Town is very sunny compared to the UK. But, the downside is in winter it rains, it gets cold. No central heating to make anything comfy. Electric heating you can forget, because of the frequent power outages.
Public transport is still in the teething stage, lots of hiccups. If you want to get somewhere reliably and safely, you must have a car with anti-hijack immobilisers etc..
The nice lifestyle comes from having a good job, for which you will have to have excellent qualifications. If you don´t have the qualifications, then being black helps. Remember, whites stand at the back of the queue when it comes to getting jobs (and a place in an old aged home).
Sure, there is crime all over, even in London. BUT, would you go into / live in these areas: Priory court, Walthamstow, Brixton, Clapham, Tooting and Stockwell, how about at night? These are similar to lots of parts of Cape Town.
If you have ticked all these above things off, and are still not daunted, then you may well be able to survive in South Africa. Being open minded, "constantly on the alert" and prepared to adapt, then you are already halfway there.