Intersting john----the boards I received have no holes, so i assumed they were fixed with adhesive, however I contacted bailey who are going to send me a diagram and SCREWS to fit the boards with ----looks like i will be drilling the holes!!Sorry to disagree with Damien but the boards I received were drilled and I fixed them with woodscrews just long enough to go through the board and batten and into the wallboard.
I can't see how this could cause damp problems unless you use screws long enough to penetrate the outer skin
Bailey certainly use screws.
But if contact adhesive works then do it that way.
I would have thought that it would be messy