You need to stick them to something. Bare brick isn't square /plumb enough.Why do you need something behind ?
You made no mention of current surface, just baton to level .Insulation would be prudentYou need to stick them to something. Bare brick isn't square /plumb enough.
I've had to square up a wall prior to fitting the pvc panel, so at the moment the surface is bare plasterboard. The panel covers the whole of the wall (1000mm wide, one side of a chimney breast) so I'm not sure what would be gained by skimming and painting the plasterboard prior to gluing the single pvc panel to it.You made no mention of current surface, just baton to level .Insulation would be prudent