Further to the OP, is there a document somewhere that spells out the requirements/specification/alternative install options for this exterior section of VDSL wiring install?

I am getting VDSL installed shortly, and my preference is for the installer not to run external conduit (as in the OP's case) to get from the barge board termination ETP to the under-floor space. I would prefer that the new VDSL CAT5/6 cable follows the existing phone line back up through the soffit and into the roof space, then down to the sub-floor space via the gap between the external brick facade and the timber framing of the adjacent interior room.

I know that this is something I'll have to discuss with the installer on the day, but I wondered if there was some reference documentation I could familiarize myself with to understand whether this is something that I can insist on or not. I want to minimise the visual impact of the install, and I know that what I want is possible, but that doesn't always mean that the install tech will want to do it that way...

Cheers