Are you sure they aren't on the key?
Spark plugs on my car aren't on the CBS but they are a servicable item, they are done every 3 oil changes which works around every 60k.
I imagine the glowplugs are the same ...
2007 330i M Sport Saloon Le Mans Blue
Active steering - Comfort Access - Bluetooth -TV - Heated Electric Memory Leather Seats - Auto - Logic 7 - Pro Nav - Adaptive Xenon Headlights
BMW Assist - iPod integration - Swirl free