the service provided by BT is poor and substandard for the BT Infinity Plus. i was initially promised 65Meg to entice me away from Sky. After an age of up and down and complaint etc. a technician visit my premises, and he confirmed maximum would be 51 Meg, then after another bought of service complaints Customer Services said best would be 45 Meg, to date I have not had this speed yet, but they continue to charge you, theft would be another word to call it.
and use this speed tester then carry out the further diagnostics and post back a screen shot of all the results including your IP profile for up and down. This test must be done with a wired connection.