Yes, there are air vents.
No, I'm not lifting the floor, or GAMI to lift it, it's too much disruption.
Having been rummaging around in the damp there's no danger I'm putting Kingspan anywhere near it.
Not sure a membrane on it's own to stop draughts will help much as the place is mostly carpeted.
I didn't realise you needed a membrane on top as well as underneath the insulation. I'm rapidly going off the idea. Sigh.