After a few weeks of carefully studying various threads on various forums and looking at youtube videos I've successfully managed to do the following coding;...... So far...

Battery replacement register including changing the AH rating.
Digital speed in the cluster.
Enable my Dension unit.
Alarm chirp on lock and unlock, including the option in the iDrive
Welcome lights fade on, ("soft_einschalten") dips, fogs, tail and number plate lights... including the option in the iDrive
Third brake light force flashing... Although I have yet to confirm it this works.
Reduced the 'fuel-reserve' level warning from quarter tank to one-eighth.