Feedback 4 years later:

Essential! It worked really well, never missed a beat and was often the difference between being able to keep driving or having to stop and let the engine cool down.

The mounting brackets and fitting was top notch from Matt Savage - thanks Matt!

In the future I might look to move the gearbox oil cooler forward and put in a bigger radiator as I think the huge intercooler does block too much air.

The only very small downside is it is very hard to get the cowling off with the fan on the inside of the radiator. Have to remove the engine fan first.

my 2/100c worth , If you are fitting a kenlowe as a standby , for the viscous fan failing , then maybe not a bad idea , belt and braces !
If you fitting it to try and boost your cooling with a perfectly good viscous fan fitted then its a waste of time , as the viscous will move far more air, and at higher speeds the ram air will do the job anyway .
A defender should not overheat if is maintained in good operating condition . I had a 130 DC HCPU in Australia that would quite happily operate in 40C+ pulling a GTW of over 7,450kg up[ long inclines . and was factory standard apart from a snorkle . HTSH

Thanks mate. What is a "DC HCPU"?

"then its a waste of time"

Certainly not my experience for my setup. In deep sand, mud and up hills that take 20 minutes to climb such as in Swaziland and Ethiopia, the engine temperature would start heading to the red, flicking on the Kenlowe would bring it down to an acceptable level again.

When leaving Sudan it was 46 degrees in the shade, my vicious did fail, but I could keep driving with the Kenlowe all the way back to Europe in the end.

If you have the large intercooler for a long trip I would say it is essential, but thanks for your thoughts as well. I did clean out the whole cooling system half way through the trip, in acid baths etc.