One day I will compare the above file with my duff user.ini file(s) and see where I went wrong. Since asking, I have bought a Zoom 7805 ATA, unlocked it and it does the job (well, sort of as it seems to drop to single duplex from time to time...).
I have a spare (functional - used it with cable, until I wrecked my user.ini) 716 if anyone's interested and adventurous
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