It's good that you can see the DPM as that means your floor is watertight and that the DPM is under the floor. You should use a proper DPC membrane for anything that touches the concrete or block. Although the 1000g DPM is similar, DPC is better. If you need something to cover the floor then use DPM but no real need as it seems to be already there. Another layer of DPM could just trap moisture. Typically a 50mm air gap is required in a cavity. I would fix the breather membrane to the inside leaf of the timber-frame in the cavity. 50mm PIR (Kingspan, Celotex, Ecotherm etc) is enough. But the more the better. Also depends on what is under the concrete floor. If there is nothing under the concrete floor then I would go 75 to 100mm at least. Other than that I would say you are on the right track.
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