Thanks Alexander, David, Bert and all.

I've got it working!

My memory of events is like this: I tried Alexander's suggestion of
print it "Smalltalk listLoadedModules". The UnixOS... didn't show up. I
copied David's compiled  version everywhere (if in doubt, copy it!). I
shut down Squeak, re-started and did "Smalltalk listLoadedModules"
again. It still didn't show up. This puzzled me. I knew it was all
there, like a sleeping daemon :-) (guess who watches too much Buffy...)
I remembered Alexander writing that it should load automatically and
used the browser to find "UnixOSProcessAccessor startUp", did it, and it
looks like everything is working: it now shows on the list generated by
"Smalltalk listLoadedModules", the Squeak Shell works fine on pwd, cal,
ls and so on. (It's also rather snappier than I'd expected). 

All rather strange, but you got me there in the end.  Many thanks.

Cheers

John
-- 
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Marx: "Why do Anarchists only drink herbal tea?"
Proudhon: "Because all proper tea is theft."
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