Thanks for the replies guys. Any reason the fan that Andrew mentioned being full on @ 12v cannot be brought down to say 50% via a resistor, I assume it is a dc motor?

I don't fancy changing my sensor/relay wiring setup around that has been reliable under all conditions, I also have dashboard indication of slow and fast, so everything is in place.

The speed controller is a nice touch and I bow to your knowledge, that is still under consideration but I too have particular requirements to suit my usage pattern.

I have trolled through 2000+ ebay adverts looking for the right fan and shroud dimensions and think I am getting somewhere, damn if I could pick up a brand new MK VIII fan I would not be bothering you guys. I have to accept I need an alternative fan option, your help is appreciated.

Regards

Dave