Replacing boot underlay/ under carpet? (LHM damaged it)

[Jaf]

I managed to pour 5 litres of LHM in the boot (a while ago, I used cat litter to soak it up, obviously didn't work). Just taken the carpet out, think that's going to be OK. The thick underlay is revolting and 1 of the 2 panels of silver thin stuff (soundproofing?) has gone soft.

I can't find any specific car carpet underlay, am wondering if I can use house stuff? Presumably both house/ car underlay are fire retardant.

Thanks.