With Infinity1 installed the download speed has fallen away again.
After having a stable rate 20-22Mb for several months, 2 weeks ago my IP profile changed, and in now capped at 17.42Mb !
Previous visits by BT engineers performed line tests and found no errors at all, FFC etc at 20Mb, only when this was raised to 30Mb did low level of errors begin to appear.
I don't want to phone the Indian helpdesk as this will no doubt end in them following their script and booking another engineers visit .... only to find no fault ! Waste of BT's time and money, not to say my time.