I worked it out last night. The creality branded bl touch loom was wired differently to what the guide indicates https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe . I bought a new bl touch and compared the terminals. I guess not all is lost, now I can install the spare bl touch on my second machine!
The guide instructions
3.3V - nil
In - White
GND - black and brown or blue
Out - Orange or yellow
+5V - Red
The creality loom from left to right(with metal terminals facing you)
white
black
yellow
red
blue
The Official BL touch loom from left to right(with metal terminals facing you)
brown
red
yellow
black
white
So in the end I connected the duet end as follows:
3.3V - Nil
In - blue
GND - red + white
Out - Yellow
+5v - black
Hopefully this will help somebody else with a creality based BL-touch.
Cheers
P