Tom, I'm really grateful, this has saved the day for me. Thanks! :)
Lon, it would be interesting to see the exercise files for that Solution Recipe - I was never able to find them and I think the link has been moved, or even removed completely, so I applied the Recipe to the default files created by SA. I wonder if someone from WebAssist could point me at them? I managed to use Show Region to hide the user level from regular visitors, but the page was still inaccessible to Admin. Clearly two different pages are needed, but SA does not provide for this - strange, as it would be needed on any password-access system I can think of. I'll send some feedback.
As you can see, Tom has solved my problem but I'm still interested to see if SecurityAssist can build a system with profiles that Admin can securely update.