As a BMW rider (for the moment) I am well accustomed to using breakdown cover. I have used the RAC and Green flag, and got better service from Green Flag who actually sent out a flatbed rather than man with a van which is what the RAC have sent out everytime. The free RAC cover you get on an MCE policy isn't enough if you intend to leave your home town at any point so you need a proper policy.
ADAC are definitley worth a look if you are willing - they subcontract out to RAC/AA/GreenFlag as needed for uk policy holders - you will need to go through a german call centre though - but they have english speaking staff there that will sort you out - you cannot apply online though. They automatically give you the "top level" cover of whatever the local breakdown company is as well.
