I have just received a phone-call to advise that although there was a snag with the initial-starting of this machine at my IT-expert - during testing, he
has subsequently taken apart the components and no obvious-fault found.
Refitted and plugged all back and started immediately and several times more with no problems.
One of the front USB-3 internal plugs was slightly loose, but not thought to be an issue.
It will be back with me tomorrow (Thursday) and hopefully problem solved and I can get-on with doing what it and the observatory-gear is meant to do - easily...

Cheers
Terry