Hi
Lots of references to marriages in the " Wheatsheaf Rooms, 263 Paisley Road" - the earliest I googled up was 1907 and into the 1940's.
http://audio32.archive.org/stream/historyofunitedc00reiduoft/historyofunitedc00reiduoft_djvu.txtThe premises was originally the "Paisley Rooms", tearooms as part of the large "United Baking Society". From this link you can elect to open up the book as a pdf (a much nicer read!)
"The address of Mr M'Culloch was published in full in the local Wheatsheaf of the Lisburn Society""...The next venture of the Federation was in Paisley Road, where, on 25th May 1895, tearooms were opened. Following on the opening of the Paisley Road premises, no alterations took place in this section of the Society's business until the end of 1897, when the comnmittee….." "…...Toward the end of 1903 the Paisley Road tearooms were destroyed by fire, and in restoring them the committee decided to add another storey. The landlord agreed to bear a proportion of the cost, and on the reconstruction being completed they were named the " Wheatsheaf " tearooms. "There is also a lengthy discussion on the viability and success of the tearooms, and then I think it says (after the main bakery business was moved to the huge St Mungos premises (a picture is in the pdf), the ailing Wheatsheaf Tearooms were bought from the United Bakery Co-op by a manageress there
This would be after 1903, and probably before 1907 as I'd guess this manager was a person, who in entrepreneurial spirit then hired out part fo the premises as a "wedding/cum reception package"
Cheers
AMBLY