R250k is not too much. Buy some RSA Retail Bonds or else consider an investment with Coronation or Allan Grey. But use it as a start and invest something each month. Compound interest will do the rest of the work for you.
Sorry but it irks me when people offer up names of asset managers as investment advice. With both those companies you have a range of portfolios ranging from conservative to aggressive to choose from. Saying invest with one of them is not advice but, seemingly, just name dropping companies that you've heard of.