Please remember that you, the end user, has no relationship with
Openreach. You have a contract with your
CP (
ISP) and it is your
CP who has a contract with
Openreach.
As I understand it, your
CP is
BT and there is where the problems will start.
Briefly, I will advise that you contact your
CP and cancel that
Openreach appointment. By my limited powers of remote divination and fault-finding, I will suggest that the fault was cased by water ingress into the network cabling which has now (predominately) dried out. I speculate that the water ingress was causing an "earth contact" fault . . . hence the noise.
Looking at the lower montage (the snapshot graphs), it seems that you have a very good 40/10 Mbps service and long may it continue.
Finally as all extension wiring "downstream" of the
NTE5/A is entirely your responsibility I would urge you to check if, indeed, any exists. It is a very simple task -- undo the two screws that hold the lower front face-plate onto the
SSFP, which in turn is fitted to the
NTE5/A and carefully remove the lower front face-plate. Any there any wires connected to its
IDCs? If no, then you do not have any extension wiring.