Daysave return Train tickets to any Southern Railway Station for 4 people - Bank Holiday weekend +

Hi I have valid train tickets (outbound and return) for 4 people travelling to any Southern Railway station for this coming weekend (25th-27thAug) - see link below for more information: http://www.southernrailwaytickets.com/buytickets/daysave/DaySave.php?sEvent=TicketDetails. I bought these tickets thinking they would get me to Plymouth and got mixed up with Portsmouth!