I hope you are ready for the £100+ bill when no fault is found.
You are seeing what hundreds of other users also see. As more properties move to VDSL crosstalk and conducted noise increases resulting in speed drops. Mine has dropped from well over 90Mbps when I was the only user, to mid/high 60s as more moved across. And one particular neighbour casues a 10Mbps drop. Can I do antything? Notreally.
M H C
taurus excreta cerebrum vincit