Although VM ‘engineers’ , shouldn’t do it , often to utilise the existing phone internal sockets , they would run a cable from the brown VM box to the grey BT/OR ‘box’ , and disconnect the BT/OR external cable from the internal cable , and then connect the internal cable to the cable that was run from the VM box, that way the VM service could ‘use’ the existing sockets , saving the VM engineer the time to run their own internal cables etc.
If the external concrete ‘step’ is being demolished by the builder doing the ‘porch’ if that is done carefully, it may be possible to simply reroute the OR cable and BT66 , the grey box, to where you want it , ( depending on if the new location is overall a shorter cable run ) but the internal cables would also need to be rerouted to the new location of the grey OR ‘BT66’ block terminal….the ‘official’ way to do it would be to run a new cable from the footpath jointbox to the house wall , a position of your chosing, and then move the internal cables moved to the new location of the BT 66, then the old cable can simply be removed by the builder ,
Do you have access to FTTP now or in the near future? Having that installed would make the other problem go away & save the expense of a move.
Not available yet, but says soon. Do they then make new connection somewhere, bit like Virgin?
Yes it would be a new fibre connection but might make use of the same duct the current copper is in. So bear that in mind when moving anything as you wouldn't want to obstruct/block the duct.
That grey openreach BT66 connection box is fed from the street by an armoured cable. This type of cable is normally direct in ground so it is not fed by any Duct work. It could be located back along the outside wall. A new cable would then need to be run from it to your phone socket.