In order to operate electric devices which require 240V, this electric power needs to be led into the vehicle. I had purchased a mains inlet, grey, a "motorhome hook up socket". This has the usual UK motorhome connection with the three round prongs. I do have adaptors for standard UK plugs and also for Central European plugs. Now all I had to do is to cut an opening into the vehicle and affix this mains inlet.
First I drilled a pilot hole from the outside. I had identified the approximate location from looking at the inside, where a side panel had been removed and was showing which area would be best accessible. After the first small pilot hole had been drilled, I used a larger drill to enlarge it. Then I used a jigsaw and started to make the straight cuts. Made lots of noise, but worked very smoothly. I had used masking tape to indicate the exact cutting location. After the rectangular opening had been cut, I used primer to cover the blank metal regions to avoid rusting. Then I used silicon gel to cover the boundary of the inlet box, before pushing it into the opening.
I also added some foam padding to ensure that a tight fit would seal the opening. 4 self-taping screws were used for affixing the box tightly to the vehicle.
This was the very first time that I cut an opening into a vehicle. Feels first as if this means doing damage... but when looking at the completed mains inlet with its flush closing watertight door, then it is clear that I actually added some value to this vehicle.
The next step will be to add the actual power cable. Need to study which of the pins in the socket/plug is to be the Load and which the Neutral.