Hi
New VM broadband TV phone installed a few months back. (long story.) Where VM cable comes in, is through the existing socket previously used for TV aerial. The backbox and faceplate were removed.

Despite this, we don't get cold air or such coming through the wall from outside. It's been through one winter and storms.
The black cable comes in for about 2 metres, and connects to this:

And then to what I think is the usual connector / splitter to router and TV:

The services are working fine. What I want to do is to sort out what's on the wall. There is a question why engineer left it so... for now I prefer to find a easy DIY solution.
My idea is to get a set of backbox with matching faceplate. Which one should I get? I thought a safe option is to get the "brush" type for cable through, that's the face plate. I still have the old backbox:

I'll get a faceplate with screw holes to match the existing backbox. That's the plan. Or find a matching face and back.
Then, I will detach the cable to install the box: unscrew the cable from the white tube thing in the second photo, put the black cable and white tube etc. through the backbox and face plates, reconnect the white tube to the white cable, and screw and tidy up the box and plate.
Am I going mad with this idea?
Thank you for any suggestions / correction.
David