Noticed that there's a new way of de-fogging double glazing without
replacing the glass. According to the details ;

Two holes are drilled, top and bottom, in the glass. Cleaning and demisting
fluid is injected into the hole and afterwards a one-way valve fitted.

Don't know how effective this method is but I'd like to give it a try. Does
anyone know where I can buy the fluid and one-way valves online (or one of
the sheds) ? Tried googling but without knowing the correct name for the
valves and fluid all I get are pages of adverts for firms who will carry out
the work for me !