Î have been given alot of poly sheets 100mm x 2.4m x1.2 m i have a woden floor between my downstairs and basement that has no insulation its a pine floor over beams any reason not to use this free insulation in this area?

I don’t know the regs but if it is traditional white/messy polystyrene, its a fire risk. It might be OK if the basement ceiling is overboarded with plasterboard…but that’ll mean its not free.

you also mustn’t put it near pvc sheathed electrical cable