On Jun 10, 11:07*pm, "george [dicegeorge]"
wrote:
I used some rough *plastering , and also mortar paint on the walls
before fitting kingspan so as to block off any draughts through tiny holes.

Since this wall is solid I do not have to repoint it.
However for waterproofing I will be using EverBuild D.P.M. which is
basically a bitumen & latex paint.

I'm wondering about a thin layer to go over the kingspan and the battens
to totally seal it, not sure what to use though.

Foil backed or moisture resistant plasterboard will seal it re damp.
As for air draughts you only need block convection, the insulation
will do that.