Wow, I posted that nearly a month ago. Yeah it seems to be either the mobo or the power supply. I think its more the mobo though because once I actually manage to start it, its fine, if the power supply was fooked then I guess I'd have more problems, but once its started, the power seems stable.
Oh well, I'll just leave it on until I can actually fix the problem, been on 3 weeks straight so far cause it usually takes me about 3 hours to get the damned thing back on and working...
As for the power cord thing, it doesn't help.
You quite litterally have to unplug components etc and its completely random. But yeah, the light thats on one of the PCI components flickers when its off. When its not flickering its fine, boots up when I short the contact (I think the button is a bit dodgy too, probs why its fooking my mobo up...)
Thanks for the posts, but unless I can get another PSU and Mobo to test with, its gonna be expensive, lol. Hope its not the PSU though as that was more expensive than the Mobo.