Doesn't sound great, unless there's a bad connection somewhere. I would think a good BMW independant garage may be able to read the fault codes from the module with a diagnostic check
Just read a thread on another site and it says the symptom is caused by the LCM and is a common problem! There is even a link to the Bentley manual LCM repair section that givews details of how to fix it! So looks like I'll be soldering soon.