Heya mate
The best thing to do would be to pass your local BMW dealership and ASK them the price of this number
0141 9 789 947 (if you cars build date is between 9/96 an 9/97)
or
0141 9 790 427 (if it is after 9/97)
if you dont know when the build date is, let me know the LAST 7 digits of Chassis details, and i can get you a spec list of the car from BMW with all the details