All done - just needed to change interfaces using serial and now all working well - and MUCH faster than the old Alix. No actual measurement of speed - but seems much more responsive.
Only strange thing - 9600 gave garbage, 38400 gave garbage, 115200 worked perfectly - watched all boios boot, then pfs starting, changed interface - loaded into pfs opening menu - all working fine. Can't understand why 115200 - the backup config loaded from old Alix was 9600.
Presume (?) that APU-1C must run at 115200 by default?
In any case this might help someone with similar problem - although I still think it should have been 9600!
Thanks for suggestions.