On Sun, 10 May 2015 11:10:49 +0100, Fredxxx wrote:

Do you english still install timber windows in the outside leaf ? .....

I haven't seen a wooden window in years. We normally use glass.

Is there some window tax or other reasons why you would fit wood to an
opening, or do you live in a poor region?

Umm, every single window and door in this house, including the four brand
new ones I've fitted to an outbuilding this year, are wooden. They were
more expensive than tupperware, too.

Going back to the original question - none of the walls are cavity,
though, so I can't comment about which leaf they're fitted to here, but
they are all fitted flushish with the outside rather than the inside, as
is normal, so if they were cavity they would be in the outside leaf.