Arrrrr got a replacement of the whole suspension unit found under the spare wheel, plugged it in and still the pump doesn't engage!!! Im going to plug in my scanner 1.4 to see if anything needs to be reset, but I guess apart from the sensors, what else is there? is there a way to test the sensors, etc. manually.

OK, slight progress, I found a thread where a guy was having similar issues and had figured out how to engage the compressor manually to fill the suspension air bags. On the compressor there is a relay, he bypassed the relay as per below pics. The pics where sourced from the thread...
http://www.xoutpost.com/bmw-sav-foru...l-pump-up.html
http://i60.tinypic.com/2qk45qr.jpg
http://i59.tinypic.com/2ronrti.jpg
This fired up the compressor, but when I checked the air pipes (red/blue) no air was coming out of them. These pipes have to travel through solenoids (one for each pipe) and it would seem the air is not passing the solenoid. I therefore looked at the solenoid and they contain a what I guess is magnetic valve that when sticking out stops the air, but when pushed in, allows the air to flow to the air bags. I therefore taped up the values, bypassed the relay and was able to pump up the air bags.

http://i62.tinypic.com/256496q.jpg
http://i60.tinypic.com/2qlqt8g.jpg
This now opened up lots more questions, what controls the solenoids to open/close? the suspension sensors? if so, do the sensors work independently or together as the chances of them both going at the same time is unlikely, of if one is out, will it not work? . The airbags, how much air are they meant to take? when full, are the firm to push in? as I don't want to over\under inflate.