I have read somewhere that the procedure was that you declared yourself married in front of witnesses, then you and the witnesses went to the Sheriff Court, and you told the Sheriff you had got married and the witnesses corroborated that, then you were given a warrant authorising the Registrar to record the marriage in his register.
So the place of marriage could have been pretty much anywhere. Your home, or a hotel, or a solicitor's offices.
There are listings of Registrar and Registration Offices in the 1907 and 1915 Valuation Rolls, but only a tiny number, so it seems probable that Registrars in most places would have had some sort of office in their home or other place of work.