In recent days a few of the items which I had ordered, arrived by mail: cables, the solar controller, battery clamps. One of the important cables it to get the 12V+ from the vehicle battery to the leisure battery, so that the alternator can charge the leisure battery. This is only the fallback option, in case there is no sun. I was able to drill a hole from the passenger compartment into the engine compartment, and I guided the thick red power cable through after securing the two holes with appropriate grommets. All that is missing is now the fuse, and then the relay for switching the two batteries together.
I did order a TEC2M relay, but then realised that this is linked to the ignition. This is not what I wanted. I rather would have one that automatically switches itself when the engine is running, that is when the alternator charges the vehicle battery. Therefore I did also order a TEC3M relay which does exactly this.
I will further install two switches: one for enabling the charge by vehicle alternator, and another for manually overriding the relay in case a connection is explicitly wanted (e.g. for recharging both batteries by the solar panel).
Today I also added window tinting to the two rear windows. The side windows in the back are actually all tinted; so to complete the privacy screen I did use the tinting foil that I got in Germany in summer. My tinting job for these two windows is, I must admit, not very professionally done. There are still bubbles, as I was not able to get rid of all the wrinkles. I guess that is because the foil appears not to be very flexible and does not stretch to the curvature of the windows.