Yes - a faulty PSU would certainly be a possibilty, however my Corsair HX 650 was working flawlessly on my old system so I dont think that is the problem at this stage, Unfortunately I dont have a lot of different Ram/ CPU's to swap out components to isolate the issue.
I have requested a service ticket from Gigabyte to see if they can offer anything.
It may still be a faulty motherboard - although I have not observed any other problems - I have raised bclk to 160 and it runs fine. The fact that some people with identical systems dont have this problem, after testing and isolating the Ram, it could really only be the CPU or board.
BTW I did remove the cmos battery and a full reset sequence and still no change.
If the issue occurs only when the PSU is actually switch off, it is feasable that some bios settings (strap?) get reset - then when I power it on it goes through this loop before booting up. Problem is, why dont other people have the same issue?
I am certain there is nothing wrong with the way the system was installed, as I have been building systems for many years, for myself and a number of my friends.