Thank you maneke exactly what was required - I called Asus to check the version, and they confirmed it was "Pro". (MS stickers don't specify, perhaps Microsoft needs to re-think this one out, because when we have a dead hdd, how does one tell?)
I have installed win 10, and boots into 10 with a couple of caveats below), so we now know it wasn't a EUFI issue but simply a corrupted hdd. MS decision in regard to failing hdd's in 10 leaves much to be desired (can be checked in Events, but when the system is dead that's not possible).
The two issues I have may be due to the way I did the clean re-install. First I copied all partitions (including the System EFI ;partition) but not the damaged system partition. I did a clean install to this unallocated space (same size as previously).
Now when I boot I have two issues I would like to clear up:
(i) On clean boot it asks me which of two Win10 options I want to boot into. The new one is the default, the old one goes to an error. As there are 30 secs to choose, one could reduce this to 0 to resolve (how?); preferably to remove the options altogether?Any advice how to resolve these two issues would be appreiated - very steep learning curve with Win10!
(ii) it is asking me for a COA license, of course we don't have one as originally it was an upgrade from 8.1 where the licence is held within EUFI?