Buying a house

We purchased a house in a gated community with minimal parking. The developer has now given a house outside of the gated community access to the community and now taking up car parking. They have also added them onto the management scheme for the community. How can they alter the deal that we agreed through our contract? They have increased the value of the other house they struggled to sell, made mine less desirable as parking is worse..... I would not have purchased if I had known this and would have definitely paid less. Surely I am protected as we had a contract?