Hi Paddy,
You seem to have enough power there, however no error beep during startup normally means motherboard or
CPU failure. - normally
CPU. From what you were describing, you were able to get into BIOS and then it froze whilst in BIOS? It sounds like the
CPU may have fried at that point.
Make sure that the case
CPU speaker is connected to the correct port on the motherboard, and then make sure that the
CPU is properly connected. Try to reseat, and check for burning smells on the
CPU and look out for capacitor leakage on the motherboard. Try your PC with just the
CPU and motherboard (no graphics or memory). Your PC will normally beep at this point. If it doesn't then it really does confirm motherboard or
CPU.
EDIT: Marked as answered.