Right, to get it working, as folks have said, you need yourself a relay- the current that fan draws will burn up the stock wiring on the ignition.
The standard four-pin 30 amp relays you can get at Halfords do work but require a little extra wiring- two quid extra gets you a nice one that has a fuse holder built into it (link at bottom).
Buy a 2 Amp fuse for the ignition barrel side. The relay comes with a green 30 Amp fuse which is good for the fan motor.
Splice one leg of the inline fuseholder into your ignition circuit, on the switched side- I like to put it on the position I because that switches off momentarily when you engage the starter, and you can also switch the ignition off but leave the fan to run when it's hot after a drive.
Run the other wire from the inline fuseholder off the ignition into the engine bay. Find a place to stick the relay (close to the battery, or the main + wire if the battery's in the boot). Connect the wire from the ignition to spade connector 85 on the relay. Connect 86 to one side of the thermo switch on the radiator. The other pin on the thermo switch goes to the vehicle body to give an earth.
These wires don't have to be very heavy gauge, about the same as you'd use for sidelights.
Choose a wire that's at least as thick as the blue wire off the fan.
Connect it to the battery +, but keep it as short as you can between there and the relay. Connect it to 87 on the relay.
I say this because the longer the run of wire, the more chance you have of cutting/chafing/melting through the wire accidentally and it not being protected by a fuse. (Burn, baby burn!)
Run the 30 connector off the relay to the blue wire on the fan, using the same or thicker gauge wire.
The black wire on the fan should be bolted to the vehicle body to give an earth.
Fit the 30A fuse to the relay and the 2A fuse to the ignition barrel fuse holder.
If you need to work on the fan, pull the 30A fuse out of the relay and it won't spin up; the 2A fuse will protect the ignition circuit if the wiring that activates the fan gets shorted out anywhere (between the ignition and the relay, mostly).
To test if it works, turn on the ignition, pull the wires off the thermo switch and touch the connectors together. The fan should spin.
www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_222501_langId_-1_categoryId_165688 <-- fused relay
www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_216687_langId_-1_categoryId_165626 <-- 10A fuse holder for ignition side
--Phil
