I eventually realised why this wouldn't work, and it boiled down to a misunderstanding on my part. No wonder there were no replies to the post - 'what on earth is he talking about!?' they must have been saying.
The includelets that I was trying to add were working fine but they were not what I thought they were. The way to get the page to look as I wanted (as per the openacs website) is to select the oacs-view template in the parameters - which I had done on a previous site a few weeks earlier!
Early senility induced by too much time spent thrashing away at websites. :-|
Richard