…a final, uncomplicated resolution to the Mac Catalina problem.
Thanks to the Audacity brains for dealing with this. They have infinitely more patience than I.
Well I’ve been testing several 2.4.0 alpha test builds - an it now seems to be fine with when in Audacity and trying initial recording I get the Apple dialog asking if I want to allow access to the mic for Audacity.
I also get, when I try ti drag& drop and audio file, an Apple message asking if I want to allow Audacity to access my desktop.
All with no recourse to the workaround using the launch of Audacity from the Terminal app. 
And many thanks go to developer Leland Lucius for cracking this for us 
Peter.