I think the pictures are self-explanatory, but feel free to add or comment accordingly...
The principle is that you need to supply 12v to Pin 1 on the Webasto multiplug - this needs to be live for as long as you want the heater to stay on (so ensure you buy a switch that latches i.e. one push for on and another for off). The software that's in the BMW system will detect low fuel level or battery voltage and shut the heater down before the levels fall dangerously low. I normally find 15-20mins is enough to warm the car and defrost the front screen before I start up. I've fitted a single LED indicator lamp, simply pushed into one of the top bonnet grills - this allows me to see that the system is active from inside the house. This is wired to the remote switch output, so only comes on when the switch is active. The permanent 12v feed that you need is best taken directly from the jump start point under the bonnet on the bulkhead just behind the heater. There is a suitable remote switch available from Maplins for around £30, but many also available from Ebay etc.
Have fun...
![Very Happy :D](./images/smilies/biggrin.gif)
![Image](http://i427.photobucket.com/albums/pp358/monkey-finger/webasto1.jpg)
![Image](http://i427.photobucket.com/albums/pp358/monkey-finger/webasto2.jpg)
![Image](http://i427.photobucket.com/albums/pp358/monkey-finger/webasto3.jpg)
![Image](http://i427.photobucket.com/albums/pp358/monkey-finger/webasto4.jpg)
![Image](http://i427.photobucket.com/albums/pp358/monkey-finger/webasto5.jpg)