Hi Monica,
I have also looked and can't find this marriage,so in desperation I contacted the Registrars office in Edinburgh and asked for their thoughts on the marriage. Here is their reply:
Patrick,
"I have searched the marriage indexes 10 years either side of the given date 4 April 1924 and cannot find this couple having been married in Scotland. It may be that they had a simple religious wedding but did not register it with their local Registrar, meaning they did not go through the legal procedure. Sorry I cannot be of further help to you".
Regards
Dorothy Ewen, Registrar
So their you are Monica,I can now only presume that if they had some sort of marriage ceremony in Scotland,(I can find no evidence of any marriage elseware within th UK) the date on my fathers birth certificate, is either the date of a as stated "simple religious wedding"which was not registered and so not recognized, or they may not have actually had any ceremony at all, and gave false details to save any embarrassment.Either way it appears that they may not have ever been legally married. I will keep on searching, maybe another relative out there has the answer. Should I find out anything of interest I will let you know.
Patrick.