I need to replace a broken window and it would seem sensible to
replace the glass with a double glazed sealed unit. The last extension
to our house already has sealed units in similar (if not identical)
wooden frames.

The glass is retained by glazing bars and there's lots of spare depth,
it could accomodate a 1cm thick unit quite happily.

Where can one buy 'one off' made to measure sealed units? (if it
works well and is easy to do I might well replace some more) I'm in
South Suffolk if that's at all relevant.

I suspect I might be supposed to get building regulations approval to
do this, or is replacing broken glass with something better OK?

--
Chris Green