I've got a shed going up next week, and I intend to insulate most of
the inside (a single skin partition will seperate out the other
section)

Now, the entire structure will be of dip treated 2x3 framing with 22mm
cladding on top (excused the mixed metrics!), on the inside of which
I'll be putting a insulating polystyrene layer topped off with
plasterboard and then a layer of plaster.

The entire building will be 18'x10' with a 13'x10' room being
insulated.

My main concern at the moment is how the plasterboard will stand up to
the expansion and contraction of the wood?

Now, my questions.

1) is this the right way to go?
2) How should I attach the plasterboard to the framing?
3) Would 75mm polystyrene be about right/too much/too little?
4) How should I run a lighting ring given the PVC/polystyrene issues?

Can you reply to the group please, I don't read the email address
provided above!