Thank you for the two prompt responses so far!
1. DasCC: The light doesn't go red when I use my 30Amp dedicated wall charger (Type 2), only yellow after 1-2 minutes and then lights go out after a while. I am at the moment using the VW-supplied cable plugged into a normal wall socket and this is working fine. So, it looks like the car isn't the problem, but using a normal socket is not a solution for me, as I need the fast wall charger to do the job (4 hours instead of 12!)...
2. dublectric: Thank you for the link - this does read like my problem... However, if a change in voltage is the culprit, I wouldn't know how to check this. Does the voltage come back to its 'normal' range after some days or should I call my energy provider?
Apologies for possibly asking silly questions, but I really do not know my way around electricity...
Any further comments or ideas?
Thank you!