Sudden dowry demand before marriage

Hi, Need your advise regarding sudden dowry demand from prospective in-laws before marriage. This party pursued us via newspaper matrimonial advt. Both the families met and liked each other and proceeded to take it further. We kept asking them about their demand or expectation from this marriage and they were like, they din't need anything apart from a wedding party and all would be upto us what we want to give our daughter. Now the scene is they made us to book the hotel by making payment worth Rs. 1,00,000 in advance and they did a informal rokka at our home. Now they are demanding huge cash and expensive gifts from us before marriage. The Prospective Groom is said to be a chief manager in Bank Of India, Head Office, Mumbai. This Groom himself came out as a dowry seeker person. So we are no more interested in this marriage and we cancelled it but want our money whatever we spent on them and hotel from them. But they are not ready to even talk so now we want to go legally. Please advice What should be done in this regarding? Thanks & Regards, CA Shikha Pathak