Renewing timber cladding

[BazzaS]

My upper back wall is cladded with T & G fitted vertically. This has warped and now needs to be replaced. I wish to replace it with Shiplap running horizontally. Currently, working from the inside out, I have plaster-board, studding, T&G. A friend says, when I've done the replacement, I should have plaster-board, studding, insulation between studding, membrane and finally Shiplap.
I'm a bit of a novice so can someone please advise:-
1) is the suggested sequence correct ?
2) what sort of insulation ?
3) what's a membrane and where do I get one ?

Thanks

 

[noseall]

from inside out;

plasterboard.

polythene vapour barrier.

timber studs and insulation.

breathable felt or otherwise.

plywood (if you want to).

cladding material.

 

[noseall]

DON'T DOUBLE POST.