Hi, I may (or may not) be able to get hold of some double glazed units
fairly cheap, probably old upvc windows. Is there any reason why I
can't use these to "knock-up" a conservatory? I'm not sure how I'd
make up the frame (steel posts?) or do the roof (polycarb with the
upvc edging stuff?)

Somebody must have thought about this before?! Conservatory
companies' prices seem to be v high.