Might just be me, but... Looking at those stats you posted...
Noise Margin, in an acceptable range. So that should be OK.
Line Attenuation, we can suggest that your line to your cabinet is either going through ~4km of copper line to reach it (from 79db) from your home, or it's experiencing a lot of issues (picking up noise) on the way to your cabinet. If it's the length of the line, nothing can be done. If it's other issues along the way, that's BTs issue, but unsure how well can they can track down issues with that distance involved. However, most services aren't offered on lines longer than 1km for VDSL2 as they rapidly lose speed, and at certain distances not offered at all, so... Unsure how that's happened (getting VDSL service with such a long line) unless if there's something causing the high line attentuation on the line. So I'm thinking it's likely something BT will need to fix (a line fault, rather than a broadband fault).
Signal Attenuation, is probably where the major thing is. Those numbers are on the border regions of having issues constantly, or not really viable for VDSL in the first place (somewhere around 45db). And your signal attentuation is near or above it. So I'm partly thinking this might just be part and parcel of the line and service you have. (Either 4km+ line or really noisey pickup, which BT either shouldn't have sold you VDSL service on, or they need to get Openreach out to try and track down where the fault is)
Someone more experience will probably be able to give you more tell you more.
If you haven't already, do what
@Caged suggested as well. See if it's something you've missed out that doesn't need to get an engineer out, since it can cost and it may not solve the issue. But personally, those stats above look like trouble to me. :-/
