There's no tax on the R20m is there??? Eish!!! I hope not.
Spend R7.5m on house, car, furniture, and other conveniences.
Spend R2.5m travelling the world.
Invest the remaining R10m.
Continue working.
_OR_
Invest the whole lot and enjoy the dividends. Roughly R66k per month (4% return) before tax.
Erring toward the former.
EDIT: Playing Powerball tomorrow!!! Buy you all beers if I win - the jackpot of course