I have now fixed the leaking skylights in my folding caravan. Not helped by the fact that they didn't use stainless screws and used silicon instead of a flexible filler. Now comes the hard part. I now need to stick the new plywood to the polystyrene on the ceiling. What I really need is a very good and quick contact adhesive so I don't need to prop it up to long. Has anybody any idea what I could use and where I can get hold of it?