Ive got to be honest im not 100 % sure my old van was lined with the same stuff! However it was done in sections, and the rockwool that i used on the last van was damp near those joins but the rest was ok. The floor was sopping wet when i lifted the wood, i think this was because of the wee leak that i had in the van and the water got under the damp proof. I am only going on advise from others, have you tried the Self Build Motor Caravanners club
http://www.sbmcc.co.uk/forum/.
Hope ive been of some help