Well to round the situation off nicely, I was clinging on to Windows 8.1 as I liked it once StartIsBack is installed (which I still use for Windows 10). But I was forced to update as Windows 8.1 told me it my shiny new processor was not supported by it (more information here) - so I bit the bullet and installed Windows 10.Thanks man. It turned out to be the PSU for me. £9 shipping for a new PSU with a 10 year warranty again, can't complain apart from the fact that it's the exact same model but I think that's just being cheeky.
Sounds like you had a far bigger mess than me!
