One more thought...
Does the VDSL/FTTC faceplate BT install work the same/a similar way to the original pre-self install ADSL faceplates?
I had an ADSL v1.0 faceplate lying in a drawer from when I originally got ADSL many years ago (nildram 512/256 for £50 a month...ow) and that has
a) lowered the attenuation from the extension wiring
b) stopped any crackling/noise when the extensions are connected.
c) given me better upload speed than i've ever seen since I was switched to sky from Be.
If the VDSL faceplate works the same way (does a similar thing) I can hopefully assume that come install day I won't have an issue?
I'm not at all sure though.