Both of your suggested clearing CMOS so I did that and that magically fixed all issues.
After removing the CMOS battery and leaving it out for 5 minutes then plugging it in again it fired up like nothing was ever wrong and the PC works normally again.
Thanks for the help!
Was playing a game on my PC during bad weather and suddenly the PC died due to a very short power cut (house lights and pc monitors flickered on and off for like a second).
Now the PC won't start at all (power button does nothing) but the wall socket and monitor has power again.
Switching the...