[Trevor]

In order to provide manual operation of the fans as you suggest simply run a lead with a switch in it to the positive side of the feed connection to the fans and connected to a fused accessory supply positive, or if direct to the battery include an inline fuse close to the battery.

I do not have a wiring diagram but would assume there is nothing else connected in parallel with the fans. If there is this item would also become energised ie switched on. I am also assuming that the fans are simply controlled by a thermostat and not via the ECU which they could well be. On second thoughts I think it would be advisable to consult a diagram before rushig into things and someone I am sure will help out in this regard.

A wiring diagram may disclose convenient connection points at the fuse and distribution box meaning that you would not have to hack into your wiring loom. It may even be possible to achieve what you require with a temporary lead with clips but there are not many exposed terminals to assist in this regard.

I started out thinking this would take only a couple of lines but in depth thought has disclosed complications.

Beav posted the address of a great site a few days ago which will give you some worthwhile electrical information.