Thanks for the response - I did look at the service manual and saw the LED flash table, although I didn't realise it was the Alienware head that I should be looking at. Since the post I retried starting the PC a few more times.....Lo and behold it restarted properly.  I am going to take this as a win and cross my fingers that it doesn't happen again. In the meantime I will look and see how to make a recovery disk based on my current windows 11 pro installation and put it somewhere safe! Once again many thanks for the response.
AWCC (Alienware Command Center) - Just got back from vacation and PC had a message that the optimization hadn't been performed in ~270 ish days and I should optimize. It went through the checks, including identifying 5 software upgrades that should be carried out including the AWCC and a bios update. I let it download all of the updates and proceeded to allow them all to install - including the bios update. Once completed it stated a restart was necessary.  I initiated the requested restart and the PC did not complete the full restart sequence - it hung (PC power was illuminated, no response from Alienware mechanical keyboard or mouse). I left it for about an hour (it had stated that only 3 mins was required for the restart) and then was forced to do a hard shutdown hold the PC power button until it shutoff. Despite trying to reboot several times I have had no success - the key board does not light up during the attempted restart sequence it just hangs with no info on the screen. Any ideas how to get it going again - it worked perfectly prior to the software update?  
Aurora R12, AWCC Software update, no boot