This search only took a couple of days to resolve once the medals arrived, however, the history behind them that has been fascinating to research.
Herbert Charles Carter was born in Australia in 1882. He was the son of Joshua Whitby Cater and Charlotte. At the out break of the Boer War he enlisted with the 2nd Victorian Mounted Rifles. His number was 342. He is mentioned on this Boer War site and the AWM. This is the official nominal roll and shows that Herbert was detached to the Pioneer Corps.
British Archives web site. The medals are quite genuine.
Herbert and his wife, Francis Alice (nee Cope) had a son also named Herbert Charles Carter. I found Herbert jnr on an Ancestry family tree and the owner very kindly connected me to Herbert's (jnr) wife.
The family story is that after the Boer War Herbert returned to Australia and was offered a solider settler block which he quickly rejected. He then returned to South Africa and is reputed to have but the first plane that was flown there. On the out break of WWI he went to England to enlist and served on submarines. After he was invalided out of the Navy he married and returned to Australia with his new family in the 1920.
Thanks to Graeme W who sent me the medals and Lynn W who put me in touch with Herbert's daughter in law.
The returned medal tally is now 1784. (There have been a few returns which I've been unable to publish the details about).