I moved into a new house about 18 months ago which has wooden double
glazing. The house is only about 9 years old, but the previous owners
had fake lead diamond effect stuck all over the windows and this,
combined with poor maintenance, seems to have resulted in the breakdown
of many of the sealed units (misted sealed units).

When I examined the windows it wasn't immediately apparent to me that
the sealed units were easily replaceable. I suppose I expected to see
some sort of putty holding them in, but it all looks like wood to me.

The windows are all awning windows (i.e. hinged across the top
horizontally, as opposed to casement windows which are hinged down one
side to open like a door). Each window has two parts - an upper and a
lower, with the upper being openable and the lower being fixed closed.
The lower parts do seem to have frames which are build into the main
frame (i.e. I might be able to remove a lower window with it's
sub-frame, if you know what I mean).

Anyway, the question is: am I likely to be able to replace just the
sealed units (the glass) or will I need to replace each sub-frame too?
Also, does anyone know of anybody offering the service of replacing
such sealed units in wooden frames?

Thanks.