Thanks for the responses and the tips.

This was solved late last night. MOBO is fine. PSU is fine.

The problem, as strange as it may sound was with the DVD drive. After unplugging various items the blinking stopped. As soon as I plugged power back into DVD, blinking started again. So, with PC powered down and AC supply shut off I opened the DVD drawer using a paper clip, opened all the way out and then closed it. Powered up and everything was fine. Love the easy fixes!