All the above said, on the VM Forum there are reciprocal posts to that of the OP.
On the VM Forum, I usually warn such posters about the perils of Aluminium last hop so that their expectations can be managed.
Btw, I did not read the OP has having already flown the BT Infinity account.
Finally, has the OP tried Executive Complaints? You can email anyone with a director handle that signs BT's letters, state your complaint politely but firmly and it becomes an Executive Complaint. I've used that route twice to get a line impairment or break properly resolved.