2 ALTON TOWERS TICKETS FOR 3/07/2012 FOR £20 OR SWAP ?

I HAVE 2 ALTON TOWERS TICKETS FOR 3RD JULY, I WOULD LIKE TO SWAP THEM FOR ANY OTHER DATES AFTER 11TH JULY DUE TO GOING ON HOLIDAY TILL THE 10TH, ALSO DON;T MIND SELLING THEM FOR £20 FOR 2.