Geoff,
The guy who writes the 'medical solutions' page for Sports Diver had a couple of diabetes questions this month (October 2003, same issue as Bob Cooper's DIR article, Tanya Streeter on the cover). I also had a quick scan of his website
www.e-med.co.uk
and there's a bit about diabetes near the top of this page:
http://www.e-med.co.uk/diving/miscellaneous.html
Cheers,
Tom