1. Firstly, you here sue the disclosed principal, the landlords. The Estate Agents have no liability in law for problems with the property. Secondly, flooding is not an "act of God". In every rental agreement or tenancy, there an implied covenant for quiet and peacable enjoyment of the property. Where the property is flooded this implied term is broken. So you have the right to sue and recover for all damage and loss suffered, such as damage to your possessions, property and furniture. Additionally, you will be entitled to compensation for seeking somewhere else to live. Finally, you will get compensation for the loss of enjoyment of the property.
2. I would suggest you either handle the claim yourself or get a solicitor on a contingency fee arrangement, as legal fees will quickly eat up the 1,000 value of the claim.