Thanks for the replies and comments folks.
Qwerty, if you mean something to prevent a build up of condensation then the 40mm gap where ceiling meets wall will have to act as a ventilation gap, otherwise I'll just have to take my chances. When I took out the internal cladding it was bone dry behind it so that gave me a lot of confidence. I was expecting black mould. There are air gaps between the insulation layers too. The space between the studs will remain open i.e. not filled with insulation. I plan on putting som small vent grills here and there so there is some air circulation behind there as well.
Goatboy, sorry the pink paint is going, same as the wallpaper. As Oldtimer said one of us has to go, and I only just arrived so I don't think it should be me.
Thanks for the tempting offer of the
pink sporks John, but I shall decline your generous offer.
Ozzy1977, you may well be right if it were in the UK the English Heritage could step in and declare it a national monument.. which is why I'm smashing and bashing out stuff as fast as I can just in case the French decide the same!
Dave-the-rave. You Sir, need to go back on the medication asap!