You ought to read RDR1 which you can find here
, in particular the sections numbered 5, 8 and 9.
If you intend to bring the money from the disposal of the property in South Africa to the UK, you will have to pay UK CGT if you have made a gain in excess of the annual CGT exemption which is currently £11,000. You may be entitled to a reduction in the taxable gain if the property was ever your main home. See HS283 here
for more information on this. Be aware that the relief for the final 36 months of ownership of a property you are not living in was reduced to the last 18 months with effect from 6 April 2014.
The basic gain is calculated by deducting the sum of the purchase price, purchase and selling costs and improvement costs from the disposal proceeds. Purchase and sale costs can include legal fees, survey fees, selling agent fees etc. Take a look here
for more information on property CGT.
Gains made on currency exchange are taxable in the UK. You will need to use the UK/South African Rand exchange rate at the time you bought the property to determine the cost for CGT purposes.
You will need to use the UK/South African Rand exchange rate at the time you sold the property to determine the sale price for CGT purposes.
Take a look here
for exchange rates. You can either use the exact rate of exchange on the dates of purchase and sale if you know them or the average rate for the year to 31 March in the tax years of purchase and disposal. The UK tax year runs from 6 April to 5 April.
You may not qualify for the CGT allowance of £11,000 if you choose to be taxed on the remittance basis for 2014/15 as opposed to paying UK tax on your worldwide income and gains. See page 52 of RDR1 here
and the notes here
According to the double tax treaty here
, you may have to pay CGT in South Africa and if you do, it will be deductible from any CGT liability you have in the UK.
I hope this helps but let me know if you have any further questions.