The backlight dimming has worked, the 3.3v & 5v connections from the Mega to the Shield are still in place, the 5v goes via a relay which switches when I turn the system on.
I have bent the LED pin on the screen at 90 degrees, cut a small slot in the shield 40 pin socket so the screen still plugs all the way in. I have then soldered on a lead to the LED added 2 resistors in series/parallel, to get 54 ohms, put a plug on the end of the lead & plugged it into the Mega 7 pin.
I have written the code so the backlight turn on at a defined brightness & can be adjusted with the left button on the Apple Ring, when I put it into sleep mode the backlight dims to defined value & turns back up if the sleep function is aborted. When the system is turned off the backlight is lowered to 0 volts.
BUT, why is there always a but? For some mystical reason the addition of the backlight dimming is playing havoc with the remote reception. After much grief I finally go the remote working every time but now it is back to misbehaving, could it be something to do with the PWM voltage that is now in the system, any advice would be greatly appreciated.