It is highly likely that there will be no consideration made for the fact there is likely to be more people heading to Ayr than usual at that time. So I would recommend avoiding rail replacements on the way down as much as possible. Waiting in the cold for a bus in paisley is not something i would wish on anyone. Even if it would mean leaving home earlier, Ayr/Prestwick have plenty of decent pubs to enjoy before the game. Enjoy the trip down guys.