I'm sure colleagues with relevant experience will email you or post here, but you may also find it helpful to have a good look through the Independent Reconfiguration Panel website. If you look at their 'completed reviews' page (http://www.irpanel.org.uk/view.asp?id=56
) their reports usually include in the appendices the original letter of referral from the HOSC/JHOSC. It would also help you identify authorities which have made referrals who you could contact for more info.
The IRP also produce a helpful report called 'Learning from Reviews' (just recently updated) which, although it doesn't go into any detail about HOSC referrals, does talk about the most common reasons for referral, the sort of issues the IRP consider, and has a section on the role of OSCs.