I have a typical victorian stylr building which i plan converting. Approved document E, part 4 gives the outlined sound proofing. For the floor ( above ceiling) it requires 2 layers of board min 8mm thick with a mass of 25Kg/m2 as a floating layer and a resilient layer min 25mm thick with a density 0f 60 100 kgm3. Would 6mm ply be sufficient as the floating floor and what economical product can be used as the 25mm resilient layer? It would need to pass a sound test.