Endulini wrote:

Do any of the North London based people who populate this group know of a
company called The Sash Window & Door Company Ltd based in Barnet? I'm
thinking of using them to do some installation and renovation to my
windows and wondered if anyone has had some experience of them (I'm making
some local inquiries as well).

Sorry, don't know anything about that.
But if I could hang a query onto yours?

Can sash windows ever be made completely air-tight.
I live in an old building with very non-air-tight large sash windows,
and have fitted secondary glazing.
But I have often wondered if I could replace or renovate the sash windows
in such a way that the heat loss through them is negligible?

--
Timothy Murphy
e-mail (80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland