See diagram he http://i11.tinypic.com/6yowscj.jpg

One of the wall in our spare bedroom has no insulation at all. It is in fact
the lower half of the wall (top half is a window) that is made up of
plasterboard over vertical studs and the back of the boards is exposed to
the roof tiles - hence the wall becomes very cold.

I can access the back of the un-insulated wall through a small door and want
to attempt to put some insulation against it. The space under the eaves is
very small (triangular shapes - height ~ 60cm, width at widest point), but I
can just about crawl there.

There is no chance of maneuvering anything rigid (i.e. kingspan) there into
position, so my plan is to put some glass wool (say 100mm) between the
studs, and secure it in place with some sort of a mesh nailed to the studs.

Any thoughts?