Thanks for your reply Nookie.
The website where you have seen information on the WILKE family is mine -
www.familyquest.bndon.comAnd all the sites that show up relate to posts and queries of mine on the family, so no joy there.
His date of birth was obtained from his WW2 War Service record on the Australian National Archives website, but apart from that I have no documentation - hence the search of the SAfrican records.
I may just give up and accept that it is correct as it would have been provided by the man himself when he enlisted.
Thanks again for your advice on this matter.
Now all I have to do is try to find information on his mother's background......

She (Gertrude Eugene MELVILLE) b. c1889 (where...??) married Walwin Harold WILKE in Doornfontain, Sth. Africa in April 1906 and came to Australia with their son Leslie aged 6 in 1913.
She returned to Sth. Africa after the death of her husband in 1953, coming back to Australia in 1960.
And that's all I know about her....
Regards
Barb