Hi all,
Thanks for your replies.
I have just emerged from a Fedora 23 upgrade and my previous reports
were not correct!
The CDs do boot when one chooses the non-UEFI option.
I have now created two partitions, one intended for rawhide and one for
23 (stable).
I can't yet explain why booting off a USB stick fails. I don't seem to
be able to choose non-UEFI boot for the USB media.
Best wishes,
RM