After months of having a [censored] connection (I will not go through again what I have had done/tested/changed routers/engineers out etc.), and after being stuck on a 4Mb cap with a sync rate of 2300 for at least 60 days, 5 days ago the router disconnected, reconnected at 5200!
WOW, here we go I thought. But then saw it was only on ADSL1. Oh well, that is better than I had.
I have had 3 disconnects since then at night (same old problem), but it stayed on the same sync rate(ish).
Today, whilst decorating, I moved my router without realising I was standing on the power cable (wires everywhere!) and pulled it out. Crikey!
After checking when it came back up, suddenly I am now sync'ed at 6500 odd, and back on ADSL2+.
Before, any disconnection like that I was immediately pushed back to the 4Mb cap.
It certainly _is_ black magic stuff.