Seems to be very variable by region, with Manchester apparently being hit particularly badly. See various threads here and at PlusNet; it looks from outside as if PlusNet are trying to sort things but can't see what is wrong.
Still getting immaculate speeds and pings here in Winchester. (Not crowing, just putting things in perspective and adding information that might eventually help PlusNet sort things out.)
Recently moved from BT Infinity 2 to PlusNet. Very happy so far.