If you're saying that increasing my download speed is all about PN responding to BT's notification, that still doesn't explain why everything drops instantly at the fault, but it's only after PN receives notification from BT, and PN's system rolls round at some point that it goes up again? Surely someone isn't manually having to flip a switch at PN?
I accept that for some reason it takes BT several days to alter the profile once the line is stable, even though it's obviously done by computer, and that PN have no control over when this happens, but once the profile has changed, it makes no sense for PN's system not to recognise it immediately and allow maximum throughput again. It seems these things are just arbitrary. As if it's just been decided that this is how long it will take rather than it having to take this long due to technical reasons. Reminds me of transferring money electronically - you know it goes through within seconds, yet the banks' "system" makes you wait several days before the money is available, thus ensuring they can use all this extra money (which is what a bank does), and don't need to pay interest on it either.
I'm not suggesting it takes PN this long (it was somewhere between 6 and 14 hours from when I last checked BT's figure) as it's back this morning.
