I'm willing to be proven wrong but I strongly doubt that there were barracks for Armed Guard crews in Glasgow or any other port. After all, each visiting ship in effect carried its own barracks: the cabins and bunks assigned to the merchant marine and Armed Guard crew members. Operating barracks would be both redundant and represent an unnecessary financial and administrative responsibility. And it would be unwise for the Armed Guard crew to be absent from their ship in case of potential or actual attack (unlikely in Glasgow to be sure but a real possibility in other ports).
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website