Using the PWM from @hooziewhatsit I have now been able to test the fan fully, and as per @feets comments it really does move a lot of air. Testing in the kitchen (as you do), anything not nailed down on the work surface started migrating towards the fan suction side!
I am working on getting a small circuit made up to allow the PWM to control my presently installed dashboard indicators to work. I have copied a diagram kindly supplied on an electronics forum however, unfortunately it does not work, clearly my soldering technique needs some work!
Glad I came across this forum purely by chance, so hats off to @feets and @hooziewhatsit and other members who have contributed.
