After a long period of general slowdown on my Inifity 2 line and the usual rebooting of the router and India telling me that my building work/ trees and/or internal wiring must be at fault. We have had no building work and no trees any where near the front of our property.
We eventually were vvisited by a special faults investigator, who found that when we had infinity installed that the wiring block in the box where the external wiring terminal ate just outside our front door was a screw terminal type and that "Inifinty" should never have any screw connections in the circuit. Block changed to gel type and speed back up to 70 Mbps from 40-45.
well done that man.