property deal without agreement

hi ,im vipul ,we have purchased around 4800sq.ft plot in central surburbs,mumbai in 2001.we had made part payments cash and cheque. since then we are in the posession of the land doin our family marble business. but the agreement was never made due to the road widnening process from the goverment the landlord kept neglecting the agreement process. and now when the road widening is done and the agreement shoud be done the landlord is demanding unneccessary money which is a huge sum, which is not genuine and nor we can pay.we are in posession of the plot doin our business with electricity bills on our name. we have also paid assessment tax in the year 2007 from our end by cheque and hold the receipt but in the name of landlord as the plot is still in their name.we have a notary done by the landloard for us to posess shop establishment certificate for our business mentioning that the land is being sold to us and the documentation is in process.we have also made temporary stuctures for our business and have shop establisment certificate too.cheque transaction is around 25percent of the deal value.right now we are in a dilemma that we shoud go for legal help or no,and if yes that what are the outs favoring us. regards, vipul munot(