PSU is one week old (everything internally is brand new)
Update and it gets weirder, I have now managed a complete install with one stick of ram and my old radeon 4850.
After the install I have placed all the sticks of ram back in and the computer continues to work fine (in so much as I have switched on and off numerous times with no issues).
If I swap the gfx card back to the 560ti the monitor comes on and says no signal then goes to standby, bizarrely my usb hdd and speakers which are both powered independently don't switch on???
I then removed the gfx card so none are installed and plugged my monitor into the motherboards hdmi slot (is it as simple as that to use the onboard 2500k gfx?) and the monitor doesn't even come on or go into standby. And for what it's worth my speakers and usb hdd remain off?
Here is the totally bizarre thing I plugged my 4850 back in and nothing, then stupidly realised that I'd not attached the DVI-D cable to the gfx, at this point my speakers and usb hdd were displaying as both switched off (no blue light on front of either), however upon inserting the DVI-D cable naturally the monitor came on, however both the speakers and the hdd powered up???
Going to continue to investigate but confused?