I am currently living in the apartment so there should be nothing outside by flat I think...
Indeed, I just took further photos which may help illustrating.
The isolator cable came today with the pack, the cable with green label and the white rectangular socket was already there which I moved in.
But I doubt that the green one is an isolator cable...
Should a VM engineer fix this? I have no idea how to book an appointment...
I am guessing that the 'Cable Simulator 4dB' in your hand in pic 4 (bottom RHS of message #3) is your incoming cable from VM.
Trace this cable and see if it goes outside your home somewhere.
Also in the same photo on the end of the bit of cable clipped to the skirting board is one of these adapters (example below) screwed onto the coax plug
If you think the cable with the 'Cable Simulator 4dB' on is the incoming cable from VM, unscrew the adapter piece from the cable clipped on the skirting board and screw the adapter into the 'Cable Simulator 4dB'. This should then allow you to attach the connector that came with your 'Quick Start' kit (which should just push fit onto the adapter).
Try that and see if you can connect.
In any event, you may want to tidy up the cables anyway, in which case you should get a VM tech in to fit a proper wall box etc. If you don't have the proper wall boxes, or cables are in the wrong place etc., I believe the tech visit should be free as part of your initial setup but would be chargeable if you wanted to change the wiring later on down the line.
If you don't fancy investigating/trying any of the above, you can call the pre-installation and delivery team on 0800 052 1734 and request a tech visit to sort it all out for you.