An interesting collection of photos there Andy -- Many thanks for posting them.

Looking at these two from the old power plant:

http://www.electricalphotos.com/showphoto.php/photo/695
http://www.electricalphotos.com/showphoto.php/photo/698

It appears that the phases were identified as green, yellow, and purple. Was that a standard color code in Germany at one time?

Also on colors, what's the green wire in this photo?

http://www.electricalphotos.com/showphoto.php/photo/728

I know the old German system was black=L, gray=N, red=E. Is the green a newer addition, or used for some other purpose at that time, such as switch loops?

I also notice from several pictures that bonding (newer wiring) all appears to be done in double-insulated cables (green/yellow with outer gray sheath):

http://www.electricalphotos.com/showphoto.php/photo/738

Is that standard practice in Germany now? Here we would usually only use single-insulated cable for bonding.

And finally for now, looking at the switch/socket combo here:
http://www.electricalphotos.com/showphoto.php/photo/751

It appears that you have to carefully align the faceplate after wiring so that the side earth contacts correctly seat within the slots. It looks kind of tricky -- Or is it one of things which just becomes easy when you're doing it all the time? (Like opening the shutters on U.K. sockets with your meter probes!)