Bit the bullet and self installed a NTE5C with Mk4 VDSL faceplate.
Stripped out the yellow existing LJU2/1a and during the process found that some muppet had DIY extended the BT 2 pair wire with a 8 pair cable and, wait for it, just joined the blue pair together by twisting and used bog standard brown shiny parcel tape where the sticky was starting to disintegrate.
Now wired without the extension wire. Yes a bit bulky but sticks out no further than the 2 transformers for the phone and Plusnet hub.
https://i.imgur.com/GlSRiNa.jpg
Sorted
Let's be careful out there !