Here's what I got:
Color: Off On
Purple: 5.16 5.16
Green: 4.11 4.10
Gray: 0.00 0
Red: 0.00 0
Oj: 0.00 0
Yellow: 0.00 0
Nothing happens when I press the power button. Guess the PSU's completely fry'd.
PSU is providing a full 5 volts to a power controller. When a power button is pressed, the Green wire must drop to less than .7 volts. It doesn't. Therefore the power supply controller never orders the PSU to power on.
Either the power supply controller is defective. A safety lockout has tripped. Or one of its inputs do not work.
The controller has a lockout protection feature. Reset that by disconnecting the power cord from the wall receptacle for two seconds. Try again.
Possible that a power switch is somehow disconnected. IOW measure between two power switch wires (use paper clips or sharp pins if necessary to probe those connections). Those wires should measure something approaching 5 volts (probably about 4.xx volts). When the switch is pressed, that 5 volts should drop to less than 0.7 volts. If no 5 volts, wires from switch to power controller may be broken or the power controller is destroyed.
Or you have an inevitable reality. Power controller was destroyed by a surge. A power strip protector did what is quite common when too close to electronics and too far from earth ground. It connected a surge into and through the motherboard. Completely bypassed protection inside the PSU. Destroyed a power controller on the motherboard.
Either the power controller lockout protection circuit was tripped. Inputs (ie power switch) was somehow damaged. Or the power controller itself was destroyed. So how would a surge get there? Happens when a protector is too close to electronics and too far from earth ground.
Finally, what those numbers report. The Purple wire is power only for electronics in a power controller. When the power switch is pressed, the temporary short tells the power controller to power on the PSU. A Green wire drops to less than 0.7 volts. The power supply increases voltages on all red, orange, and yellow wires. After about a second, the PSU reports all voltages OK by raising the Gray wire voltage to something well above 2.4 volts. The power supply controller does other checks. If power controller finds any problems (gray wire or others), then it immediately powers off the PSU. (Your never saw the red, orange, or yellow wires move.) Otherwise the power controller next tells the CPU to execute the BIOS.
Since the Green wire does not drop to near zero, then PSU cannot do anything. Since red, orange, and yellow wires did not rise, then all problems lie in the power controller or its inputs (ie switch).
NOOOOOOOO WAY !!!!! WTF
Anyway you have to understand we have a LOT more land to cover also. Above ground is far cheaper and faster. Plus the UK is not really a lighting capital. You need to look more at France for a better idea.
but check if some parts work? 
