The bottom of the seat pans were lined with something I can best describe as mixture of asphalt, horse hair and cork (same stuff that was on the floors but thinner, maybe about 5mm or 1/4 in thick). I was not able to find any such material and will be trying the Nitrolite instead.
Furthermore, the whole seat area (back and seat pans) was covered by grey felt, about 1/8 in thick, that stopped near the wheel well (see attached image). Again, I'm thinking of using Nitrolite for this.
Not to my knowledge. All I can see is that undercoating has been sprayed in this area.