On Sun, 25 Jul 2010 01:05:42 -0700 (PDT), andrew
wrote:

I would have used an insulated plasterboard - something like the Knauf
Thermal Laminate Plus at 27mm total thickness.

That would have been ideal, what a shame I didn't know about it when I
began!

I'll have to phone around to see who stocks 6mm plasterboard tomorrow.
I think only Lafarge make it.

Thanks.