george wrote:
i bought a thermometer gun from maplins,
you point it at a wall
and it tells you the temperature.
useful for showing where insulation is worth doing,
in my case the top few feet of the walls seems to leak heat through the
edge of the roof.

Might be worth investigating how your cavity walls are closed at the
top: originally this was done with brick which creates a cold bridge
that is difficult to elimate. You sometimes can see this from outside as
a course of brick "ends" just below the soffits.