Ply wood for van lining (Cinderford, Forest of Dean)

Any size would be helpful. I'm doing up a bus to live in as I'm pretty poorly, can't afford rent and don't want to live in a town! The main cost seems to be the wood for covering up the insulation so I just wanted to see if anyone had any spare from projects that I could put to good use! Thanks so much in advance, hopefully, Pip 😊