Producer looks interesting, and I see now that CocoaSqueak comes with the 
usual guarantees about open source ;-)

Diter, Karl, thank you both for the pointers (!) no pun intended. I have 
downloaded 'producer' and will try to find time to stuff it on one's head.
.. like Homer, I have to get rid of stuff first.

I once more bury myself under self-inflicted learning curves never to be 
seen again...

Sean.