After a bit of research, here's what we posted on uk.rec.cycling:
We have recently heard from Armer Quality Components Ltd. They say: "We manufacture our own range of covered cycle shelters at very competitive prices. We also offer our own team of CHAS registered fitters for installation work." Visit their website, armerqc.co.uk where you can find their street furniture page with a couple of cycle shelter options.
In reply, Martin Gerritsen posted a Dutch site (http://www.falco.nl/en.htm which makes all sorts of outdoor furniture. Unfortunately its extensive range of funky cycle parking systems doesn't include roofing, and the shelters it does stock in another section don't appear to be compatible.
Dave Holladay at the CTC is apparently an engineer specialising in bike infrastructure, so might be worth contacting.
Sustrans has some invaluable advice on putting together a School Travel Plan, which a school should do to identify and solve problems associated with the school journey. As an online example, Devon County Council has put together the Devon Young Transnet which features advice and surveys, plus lesson plans.
Rackingplus.com has a range of bike fixings, such as Sheffield stands for around £70. It also has a page of bike shelters and accessories, but no pictures I'm afraid.