Non re-payment of Advance amount of Agreement to sell

I being Purchaser entered in to an agreement with Sellers for purchasing constructed property on 26.12.15, for a total consideration of Rs.35,00,000/-, wherein during the execution of the agreement I have paid Rs.5,00,000/- in cash and lateron Rs.3,00,000/- in Cheque. it is agreed in the agreement by sellers to provide me all relevant documents required to Bank for availing home loan. Wherein, later on it is found that there is deviation in construction against approved plan. In this matter two times my approved eligible home loan got cancelled. Like this matter was getting draged on for almost 2.5 years with various reasons and excuses from sellers. Now I am insisting for Refund of money with interest wherein the seller not responding properly. In this effect i have approached police station, wherein the PSI refusing to register the complaint and FIR it , and further he claims as the fault is from the purchaser as being a purchaser he has not verified the documents and given advance to cheater or criminal seller, and also its too long time of 2.5Yrs.