2x Alton towers for 27/06/12 but will swap for 2x alton towers tickets for 18/09/12 ?

The face price of there tickets are 84. They are from the sun newspaper and are 2 free entries for adults/children to alton towers on that date only (27/06/2012). I would preferably want to swap for 2x entries on the 18 sept 2012 but will sell for 30. Can be delievered or collected, delivery may cost extra.