AGPA cancellation - legal advice

DearSir/madam, Please suggest me on the below legal issue to proceed. 1) I did AGPA of a openland of mine to a Party X in Nov 2012 and he had provided the 2 post dated cheques of 3 months delayFeb 2013 date and paid partial amount in cash. >Post datedcheques were mentioned In the GPA registration doc.. > Issued Cheques got Bounced when i tried to depositthem and corresponding Bank provided me the 3 MEMOS with Insufficient funds remark. > Now the party is approaching me togive the when i had give an Protest petition to Sub registrar. > As the main purpose of selling my land at cheaper rate is not serverd by the party i want to cancel the GPA and retrurn back the partial amount paid by the party X who is actually a big real estate businessman with stron financial and muscle power > Can you please let me how should i proceed on legal action against the party and get my Land back as per the registered agreement.