Well this has been a lot of fun, power cut part way through the rebuild really didn't help matters even before the really hot CPU running issues and random shutdowns. Touch wood cleaning the contacts, new thermal paste and re-seating the heat sink has solved the problem.
Also silly me when I was in a little mess sorting out a new motherboard I forgot at least one option I needed as in two digital audio outputs, only have one now so it's feeding the amp and I'm using old fashioned analogue for the desktop.
You try to save a little money by buying lower spec kit and there you go, should have gone for the uber deluxe model like I did with the previous board:)
I have finally managed to watch Dr. Horrible which when you get right down to it was the catalyst for the fun I've had, probably a co-incidence but....