Hi Stephanie I'm in Adelaide and for about 7 years now I have been doing free research for people looking for information from our records re ancestors who came here.I saw your request re a marriage of Royston Brown & Irfene Barnes, and you asked the question "Did they marry in S.A.?"
The answer is definately YES.Here's the details from their marriage record.
Royston Brown aged 31yrs, single, son of Sydney Herbert Brown married 27th April 1925 to Irene Barnes, aged 24yrs, single, father's name not recorded at the Registry Office, Adelaide Dis. Adelaide referenced b303 p454. (If you wanted to obtain the marriage certificate, quoting the above. ref. nos. will get the certificate for you at a cheaper rate.
I cannot look for any children of the above union, as our birth records only go to 1906.
If there is anything else I can do for you in the future, please don't hesitate to ask. I try to get to the library once a week, and researching is my favourite hobby.