The country's services sector recorded another sharp rate of expansion in business activity in January, however it was slightly weaker than December's eight-month high.
New order growth and improving economic conditions were reportedly behind the latest increase in growth.
Investec's Services PMI was little changed at 59.8 in January from the previous month's rate of 60.4.
The index monitors the business services, financial services, travel and tourism, and technology, media and telecommunications industries.
Investec said the rate of new order growth in the services sector accelerated in January and was "substantial". The securing of new contracts, favourable economic conditions and the launch of new services all reportedly supported the increase.
New business from abroad also increased, but Investec noted that the rate of expansion eased to the slowest since August last year.
Meanwhile, additional workloads, and the prospect of further increases in coming months, encouraged services companies to raise staffing levels for the 65th month running in January.
However, the rate of job creation eased to an eight-month low, Investec noted.
Today's survey also showed that expectations of further improvements in domestic economic conditions, along with predictions of greater foreign tourism, supported optimism that activity will continue to rise over 2018.
It noted that sentiment strengthened to a four-month high in January.