Thank you for obtaining those photographs. They help but also disclose more unknowns!
Looking at "
mainsoc x.png" we can see that there is a connection to the IDCs on the lower front face-plate made using the "blue/white & white/blue" pair.
Looking at "
mainsoc y.png" we can see that the NTE5/A is connected using the "orange and white" pair. Exactly as I would expect for either an aerial or underground service feed.
Looking ar "
mainsoc z.png" we see that there appears to be three cables within the backing box. One cable contains the "orange & white" pair that feeds the NTE5/A. A second pair from that same cable appears to be "green & black"; the third pair appears to be "blue & brown". However we can also see a "red & grey" pair. To add to the confusion, there is clear evidence of more recent internal cabling present . . . CW1308 specification cable with three pairs: a "blue/white & white/blue", a "orange/white & white/orange" and a "green/white & white/green" pairs! The "blue/white & white/blue" pair is that connected to the lower front face-plate, shown in "
mainsoc x.png" and noted above.
Going back to the photograph attached to
Reply #44 which shows an
LJU2/1A, a
master socket, in use as an extension, we see it is connected using a "brown/white & white/brown" pair.
I have absolutely no idea from whence that pair emanates.
It is all quite complex and confusing. But would be fun to "sort out" and fix. Unfortunately Hampshire is too far away, for this grumpy old kitteh's paws, and it is outside the trundling distance for "
Walter's Wheelbarrow".
I am very hesitant to say any more . . . for remote diagnosis is fraught with mishaps. Certainly I have seen enough to say that there is something abnormal with the circuit's wiring within your home. Perhaps, when time permits,
Black Sheep will offer his professional opinion as to what might be done.