Ok, I've had a thought regarding the problem.
I installed twice, first time I chose wrong audio device and the install reported errors.
Second time I selected the correct device and no errors were reported.
Is there a possibility that the blootloader from the first install is still there and that's what is creating the problem?
If thats the case, then deleting all partitions and reformatting with a different OS (eg Windoze) will kill off the old bootblock and I can then start fresh again?