To this
techno-cat, it does read as if you may have star wiring that radiates from a junction box in your roof space.
However you
do have a master socket (the
LJU4/1A) . . . what you meant to say is that you do not have an
NTE5/A. As long as you ensure that
Plusnet order the home wiring solution at the same time as they order the
FTTC service from
Openreach, then I cannot see you being required to pay any extra charges.
I concur with
Black Sheep (our very own serving
Openreach technician) that it should be a straightforward task --
(1) Enter roof space and examine the connections in the junction box. Re-make the connections so that the incoming pair is fed just to your study/computer room and that a second pair to the same location is connected to all the other extension sockets.
(2) In the study/computer room, fit an
NTE5/A in place of the current
LJU4/1A. The incoming pair will now be terminated at the
NTE5/A. The
Openreach back plate would then be fitted to the backing-box. The second pair, which returns back into the roof space junction box & provides the telephony feed to the extension sockets would be connected to the lower front face plate of the
NTE5/A and an interstitial
SSFP (service specific face plate) would be mounted between the two parts of the
NTE5/A.
Job done.
Edited to add: As for your possible speeds on a VDSL2 based service, it really depends upon the length of your line to the
PCP and the type of metal used for the pair. In other words, it depends upon the attenuation of the line between your master socket and the
PCP. Do you know the location of the
PCP through which your line is connected? If so, what is its approximate distance from your home? What is the line length from the exchange to your home? What is your line attenuation for your current service?
With all the above information, our wise one --
Bald_Eagle1 -- should be able to give you a real world estimate of the throughput speed you might expect to obtain with a
VDSL2 based service.